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  • 1.
    Abdullaev, Farakhulla
    et al.
    Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal.
    Konotop, V. V.
    Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal.
    Ögren, Magnus
    Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Sørensen, M. P.
    Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Zeno effect and switching of solitons in nonlinear couplers2011In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, no 23, p. 4566-4568Article in journal (Refereed)
    Abstract [en]

    The Zeno effect is investigated for soliton type pulses in a nonlinear directional coupler with dissipation. The effect consists in increase of the coupler transparency with increase of the dissipative losses in one of the arms. It is shown that localized dissipation can lead to switching of solitons between the arms. Power losses accompanying the switching can be fully compensated by using a combination of dissipative and active (in particular, parity-time-symmetric) segments.

  • 2.
    Abdullaev, Fatkhulla
    et al.
    Physical-Technical Institute, Uzbek Academy of Sciences, Tashkent, Uzbekistan; Instituto de Fisica Teorica, Universidade Estadual Paulista Júlio de Mesquita Filho, São Paulo, Brazil.
    Ögren, Magnus
    Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens Lyngby, Denmark.
    Sørensen, M. P.
    Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens Lyngby, Denmark.
    Faraday waves in quasi-one-dimensional superfluid Fermi-Bose mixtures2013In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 87, no 2, article id 023616Article in journal (Refereed)
    Abstract [en]

    The generation of Faraday waves in superfluid Fermi-Bose mixtures in elongated traps is investigated. The generation of waves is achieved by periodically changing a parameter of the system in time. Two types of modulations of parameters are considered: a variation of the fermion-boson scattering length and the boson-boson scattering length. We predict the properties of the generated Faraday patterns and study the parameter regions where they can be excited.

  • 3.
    Abdullaev, Fatkhulla
    et al.
    Physical-Technical Institute, Uzbek Academy of Sciences, Tashkent, Uzbekistan; CNH, Universidade Federal do ABC, Santo André, Brazil.
    Ögren, Magnus
    Örebro University, School of Science and Technology. Nano Science Center, Department of Chemistry, University of Copenhagen, København, Denmark.
    Sørensen, Mads-Peter
    Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens Lyngby, Denmark.
    Collective dynamics of Fermi-Bose mixtures with an oscillating scattering length2019In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 99, no 3, article id 033614Article in journal (Refereed)
    Abstract [en]

    Collective oscillations of superfluid mixtures of ultra cold fermionic and bosonic atoms are investigated while varying the fermion-boson scattering length. We study the dynamics with respect to excited center of mass modes and breathing modes in the mixture. Parametric resonances are also analyzed when the scattering length varies periodically in time, by comparing partial differential equation (PDE) models and ordinary differential equation (ODE) models for the dynamics. An application to the recent experiment with fermionic Li-6 and bosonic Li-7 atoms, which approximately have the same masses, is discussed.

  • 4.
    Andrén, Daniel
    et al.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Shao, Lei
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Länk, Nils Odebo
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Acimovic, Srdjan S.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Johansson, Peter
    Örebro University, School of Science and Technology. Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Käll, Mikael
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Probing Photothermal Effects on Optically Trapped Gold Nanorods by Simultaneous Plasmon Spectroscopy and Brownian Dynamics Analysis2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 10, p. 10053-10061Article in journal (Refereed)
    Abstract [en]

    Plasmonic gold nanorods are prime candidates for a variety of biomedical, spectroscopy, data storage, and sensing applications. It was recently shown that gold nanorods optically trapped by a focused circularly polarized laser beam can function as extremely efficient nanoscopic rotary motors. The system holds promise for-applications ranging from nanofluidic flow control and nanorobotics to biomolecular actuation and analysis. However, to fully exploit this potential, one needs to be able to control and understand heating effects associated with laser trapping. We investigated photothermal heating of individual rotating gold nanorods by simultaneously probing their localized surface plasmon resonance spectrum and rotational Brownian dynamics over extended periods of time. The data reveal an extremely slow nanoparticle reshaping process, involving migration of the order of a few hundred atoms per minute, for moderate laser powers and a trapping wavelength close to plasmon resonance. The plasmon spectroscopy and Brownian analysis allows for separate temperature estimates based on the refractive index and the viscosity of the water surrounding a trapped nanorod. We show that both measurements yield similar effective temperatures, which correspond to the actual temperature at a distance of the order 10-15 nm from the particle surface. Our results shed light on photothermal processes on the nanoscale and will be useful in evaluating the applicability and performance of nanorod motors and optically heated nanoparticles for a variety of applications.

  • 5.
    Bergström, Per
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner Dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization2014In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, no 1, p. 123-131Article in journal (Refereed)
    Abstract [en]

    This paper discusses the possibility of evaluating the shape of a free-form object in comparison with its shape prescribed by a CAD model. Measurements are made based on a single-shot recording using dual-wavelength holography with a synthetic wavelength of 1.4 mm. Each hologram is numerically propagated to different focus planes and correlated. The result is a vector field of speckle displacements that is linearly dependent on the local distance between the measured surface and the focus plane. From these speckle displacements, a gradient field of the measured surface is extracted through a proportional relationship. The gradient field obtained from the measurement is then aligned to the shape of the CAD model using the iterative closest point (ICP) algorithm and regularization. Deviations between the measured shape and the CAD model are found from the phase difference field, giving a high precision shape evaluation. The phase differences and the CAD model are also used to find a representation of the measured shape. The standard deviation of the measured shape relative the CAD model varies between 7 and 19 μm, depending on the slope.

  • 6.
    Bergström, Per
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Single Shot Shape Evaluation Using Dual-Wavelength Holographic Reconstructions and Regularization2014In: Fringe 2013: 7th International Workshop on Advanced Optical Imaging and Metrology / [ed] Wolfgang Osten, Springer Berlin/Heidelberg, 2014, p. 103-108Conference paper (Refereed)
    Abstract [en]

    The aim of this work is to evaluate the shape of a free form object using single shot digital holography. The digital holography results in a gradient field and wrapped phase maps representing the shape of the object. The task is then to find a surface representation from this data which is an inverse problem. To solve this inverse problem we are using regularization with additional shape information from the CAD-model of the measured object.

  • 7.
    Corboz, Philippe
    et al.
    School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Ögren, Magnus
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Kheruntsyan, Karén
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Corney, Joel F.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Phase-space methods for fermions2013In: Quantum Gases: Finite Temperature and Non-Equilibrium Dynamics / [ed] Davis, M.; Gardiner, S.; Proukakis, N.; Szymańska, M., London: Imperial College Press, 2013, p. 407-416Chapter in book (Other academic)
    Abstract [en]

    We review phase-space simulation techniques for fermions, showing how a Gaussian operator basis leads to exact calculations of the evolution of a many-body quantum system in both real and imaginary time. We apply such techniques to the Hubbard model and to the problem of molecular dissociation of bosonic molecules into pairs of fermionic atoms.

  • 8.
    Hajizadeh, Faegheh
    et al.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden; Department of Physics, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran.
    Shao, Lei
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Andrén, Daniel
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Johansson, Peter
    Örebro University, School of Science and Technology. Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Rubinsztein-Dunlop, Halina
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden; Quantum Science Laboratory, School of Mathematics and Physics, The University of Queensland, Brisbane QLD, Australia.
    Käll, Mikael
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Brownian fluctuations of an optically rotated nanorod2017In: Optica, ISSN 2334-2536, Vol. 4, no 7, p. 746-751Article in journal (Refereed)
    Abstract [en]

    Gold nanorods can be optically trapped in aqueous solution and forced to rotate at kilohertz rates by circularly polarized laser light. This enables detailed investigations of local environmental parameters and processes, such as medium viscosity and nanoparticle-molecule reactions. Future applications may include nanoactuation and single-cell analysis. However, the influence of photothermal heating on the nanoparticle dynamics needs to be better understood in order to realize widespread and quantitative use. Here we analyze the hot Brownian motion of a rotating gold nanorod trapped in two dimensions by an optical tweezers using experiments and stochastic simulations. We show that, for typical settings, the effective rotational and translational Brownian temperatures are drastically different, being closer to the nanorod surface temperature and ambient temperature, respectively. Further, we show that translational dynamics can have a non-negligible influence on the rotational fluctuations due to the small size of a nanorod in comparison to the focal spot. These results are crucial for the development of gold nanorods into generic and quantitative optomechanical sensor and actuator elements. (C) 2017 Optical Society of America

  • 9.
    Kavoulakis, G. M.
    et al.
    Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Yu, Y.
    Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Ögren, Magnus
    Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Reimann, S. M.
    Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Superfluidity in a gas of strongly interacting bosons2006In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 76, no 2, p. 215-221Article in journal (Refereed)
    Abstract [en]

    We consider small systems of bosonic atoms rotating in a toroidal trap. Using the method of exact numerical diagonalization of the many-body Hamiltonian, we examine the transition from the Bose-Einstein condensed state to the Tonks-Girardeau state. The system supports persistent currents in a wide range between the two limits, even in the absence of Bose-Einstein condensation.

  • 10.
    Khodadad, Davood
    Örebro University, School of Science and Technology. Experimental Mechanics, Luleå University of Technology, Luleå, Sweden.
    Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement2019In: International Journal of Optics, ISSN 1687-9384, E-ISSN 1687-9392, Vol. 2019, article id 4906109Article in journal (Refereed)
    Abstract [en]

    We present a digital holographic method to increase height range measurement with a reduced phase ambiguity using a dual-directional illumination. Small changes in the angle of incident illumination introduce phase differences between the recorded complex fields. We decrease relative phase difference between the recorded complex fields 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈300  . Further, numerical refocusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

  • 11.
    Khodadad, Davood
    Örebro University, School of Science and Technology. Experimental Mechanics, Luleå University of Technology, Luleå, Sweden .
    Phase-derivative-based estimation of a digital reference wave from a single off-axis digital hologram2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 7, p. 1663-1669Article in journal (Refereed)
    Abstract [en]

    This paper describes a method to obtain an estimated digital reference wave from a single off-axis digital hologram that matches the actual experimental reference wave as closely as possible. The proposed method is independent of a reference flat plate and speckles. The digital reference wave parameters are estimated directly from the recorded phase information. The parameters include both the off-axis tilt angle and the curvature of the reference wave. Phase derivatives are used to extract the digital reference wave parameters without the need for a phase unwrapping process. Thus, problems associated with phase wrapping are avoided. Experimental results for the proposed method are provided. The simulated effect of the digital reference wave parameters on the reconstructed image phase distribution is shown. The pseudo phase gradient originating from incorrect estimation of the digital reference wave parameters and its effect on object reconstruction are discussed.

  • 12.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Amer, Eynas
    Luleå University of Technology, Luleå, Sweden.
    Gren, Per
    Luleå University of Technology, Luleå, Sweden.
    Melander, Emil
    Uppsala University, Uppsala, Sweden.
    Hällstig, Emil
    Fotonic, Stockholm, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Single-shot dual-polarization holography: measurement of the polarization state of a magnetic sample2015In: VI International Conference on Speckle Metrology, SPIE - International Society for Optical Engineering, 2015, Vol. 9660, article id 96601EConference paper (Refereed)
    Abstract [en]

    In this paper a single-shot digital holographic set-up with two orthogonally polarized reference beams is proposed to achieve rapid acquisition of Magneto-Optical Kerr Effect images. Principles of the method and the background theory for dynamic state of polarization measurement by use of digital holography are presented. This system has no mechanically moving elements or active elements for polarization control and modulation. An object beam is combined with two reference beams at different off-axis angles and is guided to a detector. Then two complex fields (interference terms) representing two orthogonal polarizations are recorded in a single frame simultaneously. Thereafter the complex fields are numerically reconstructed and carrier frequency calibration is done to remove aberrations introduced in multiplexed digital holographic recordings. From the numerical values of amplitude and phase, a real time quantitative analysis of the polarization state is possible by use of Jones vectors. The technique is demonstrated on a magnetic sample that is a lithographically patterned magnetic microstructure consisting of thin permalloy parallel stripes.

  • 13.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Bergström, Per
    Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holography: single shot calibration2014In: Interferometry XVII: Techniques and Analysis / [ed] Katherine Creath, Jan Burke & Joanna Schmit, SPIE - International Society for Optical Engineering, 2014, Vol. 9203, article id 920305Conference paper (Refereed)
    Abstract [en]

    In an on line shape measurement in disturbed environment, use of many wavelengths in order to avoid phase ambiguity may become a problem as it is necessary to acquire all holograms simultaneously due to environmental disturbances. Therefore to make the shape data available the different holograms have to be extracted from a single recorded image in spectral domain. Appropriate cut areas in the Fourier method are therefore of great importance for decoding information carried by different wavelengths. Furthermore using different laser sources, induces aberration and pseudo phase changes which must be compensated. To insure any phase change is only because of the object shape, calibration is therefore indispensable. For this purpose, effects of uncontrolled carrier frequency filtering are discussed. A registration procedure is applied using minimum speckle displacements to find the best cut area to extract and match the interference terms. Both holograms are numerically propagated to a focus plane to avoid any unknown errors. Deviations between a reference known plate and its measurement are found and used for calibration. We demonstrate that phase maps and speckle displacements can be recovered free of chromatic aberrations. To our knowledge, this is the first time that a single shot dual wavelength calibration is reported by defining a criteria to make the spatial filtering automatic avoiding the problems of manual methods. The procedure is shown to give shape accuracy of 35ÎŒm with negligible systematic errors using a synthetic wavelength of 1.1 mm.

  • 14.
    Khodadad, Davood
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Bergström, Per
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Fast and robust automatic calibration for single-shot dual-wavelength digital holography based on speckle displacements2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 16, p. 5003-5010Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to describe a fast and robust automatic single-shot dual-wavelength holographic calibration method that can be used for online shape measurement applications. We present a model of the correction in two terms for each lobe, one to compensate the systematic errors caused by off-axis angles and the other for the curvature of the reference waves, respectively. Each hologram is calibrated independently without a need for an iterative procedure or information of the experimental set-up. The calibration parameters are extracted directly from speckle displacements between different reconstruction planes. The parameters can be defined as any fraction of a pixel to avoid the effect of quantization. Using the speckle displacements, problems associated with phase wrapping is avoided. The procedure is shown to give a shape accuracy of 34 μm using a synthetic wavelength of 1.1 mm for a measurement on a cylindrical test object with a trace over a field of view of 18  mm×18  mm.

  • 15.
    Khodadad, Davood
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Bergström, Per
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Single Shot Dual-Wavelength Digital Holography: Calibration Based on Speckle Displacements2014In: International Journal of Optomechatronics, ISSN 1559-9612, Vol. 8, no 4, p. 326-339Article in journal (Refereed)
    Abstract [en]

    We present a calibration method which allows single shot dual wavelength online shape measurement in a disturbed environment. Effects of uncontrolled carrier frequency filtering are discussed as well. We demonstrate that phase maps and speckle displacements can be recovered free of chromatic aberrations. To our knowledge, this is the first time that a single shot dual wavelength calibration is reported by defining a criteria to make the spatial filtering automatic avoiding the problems of manual methods. The procedure is shown to give shape accuracy of 35 µm with negligible systematic errors using a synthetic wavelength of 1.1 mm.

  • 16.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Hallstig, Emil J.
    Optronic, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients2013In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 52, no 10, article id 101912Article in journal (Refereed)
    Abstract [en]

    A new method to measure shape by analyzing the speckle movements in images generated by numerical propagation from dual-wavelength holograms is presented. The relationship of the speckle movements at different focal distances is formulated, and it is shown how this carries information about the surface position as well as the local slope of the object. It is experimentally verified that dual-wavelength holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve the object shape. From a measurement on a cylindrical test object, the method is demonstrated to have a random error in the order of a few micrometers.

  • 17.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Shape reconstruction using dual wavelength digital holography and speckle movements2013In: Optical Measurement Systems for Industrial Inspection VIII / [ed] Peter H. Lemann, Wolfgang Osten & Armando Albertazzi, SPIE - International Society for Optical Engineering, 2013, Vol. 8788, article id 878801Conference paper (Refereed)
    Abstract [en]

    A new technique to measure depth based on dual wavelength digital holography and image correlation of speckle movements is demonstrated. By numerical refocusing of the complex optical field to different focus planes and by measuring the speckle movements caused by a wavelength shift both the object surface position and its local slope can be determined. It is shown how the speckle movement varies linearly with the surface slope, the wavelength shift and the distance of the numerical propagation. This gives a possibility to measure the slope with approximately the same precision as from the interferometric phase maps. In addition, when the object surface is in focus there is no speckle movement so by estimating in what plane the speckle movement is zero the absolute surface position can be measured.

  • 18.
    Khodadad, Davood
    et al.
    Experimental Mechanics, Luleå University of Technology, Sweden.
    Sjöberg, T.
    Division of Mechanics of Solid Materials, Luleå University of Technology, Sweden.
    A nondestructive validation of reverse impact experiment based on shape measurement using high speed photographs2013In: 2013 International Conference on Advanced Optoelectronics and Lasers (CAOL 2013), IEEE, 2013, p. 322-324Conference paper (Refereed)
    Abstract [en]

    High speed photography of a reverse impact scenario was taken in order to make shape measurement. The results from the shape measurements were then compared with results from numerical simulations in order to evaluate the possibility to use noncontact shape measurement as a validation tool in future simulations.

  • 19.
    Khodadad, Davood
    et al.
    Department of Physics and Electrical Engineering, Linnaeus University, Växjö, Sweden.
    Tayebi, Behnam
    Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.
    Shape Measurement Based on Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements2018In: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Electromagnetics Academy , 2018, p. 184-189Conference paper (Refereed)
    Abstract [en]

    We present a dual-directional illumination digital holographic method to increase height range measurement with a reduced phase ambiguity. Small change in the illumination angle of incident introduce phase difference between the recorded complex fields. We decrease relative phase difference between the recorded complex field 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈ 300μm. Further, numerical re-focusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

  • 20.
    Lettenström, Frans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Uppsala, Sweden.
    A study of nuclear effects in deep inelastic muon scattering1988Doctoral thesis, monograph (Other academic)
  • 21.
    Länk, Nils Odebo
    et al.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Johansson, Peter
    Örebro University, School of Science and Technology. Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Käll, Mikael
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Directional scattering and multipolar contributions to optical forces on silicon nanoparticles in focused laser beams2018In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 22, p. 29074-29085Article in journal (Refereed)
    Abstract [en]

    Nanoparticles made of high index dielectric materials have seen a surge of interest and have been proposed for various applications, such as metalenses, light harvesting and directional scattering. With the advent of fabrication techniques enabling colloidal suspensions, the prospects of optical manipulation of such nanoparticles becomes paramount. High index nanoparticles support electric and magnetic multipolar responses in the visible regime and interference between such modes can give rise to highly directional scattering, in particular a cancellation of back-scattered radiation at the first Kerker condition. Here we present a study of the optical forces on silicon nanoparticles in the visible and near infrared calculated using the transfer matrix method. The zero-backscattering Kerker condition is investigated as an avenue to reduce radiation pressure in an optical trap. We find that while asymmetric scattering does reduce the radiation pressure, the main determining factor of trap stability is the increased particle response near the geometric resonances. The trap stability for non-spherical silicon nanoparticles is also investigated and we find that ellipsoidal deformation of spheres enables trapping of slightly larger particles.

  • 22.
    Mäkeläinen, Suvi
    et al.
    Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Gòdia, Marta
    Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Hellsand, Minas
    Department of Neuroscience, Uppsala University, Uppsala, Sweden.
    Viluma, Agnese
    Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Hahn, Daniela
    Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Makdoumi, Karim
    Örebro University, School of Medical Sciences. Department of Ophthalmology.
    Zeiss, Caroline J.
    Yale University School of Medicine, New Haven, Connecticut, United States of America.
    Mellersh, Cathryn
    Yale University School of Medicine, New Haven, Connecticut, United States of America.
    Ricketts, Sally L.
    Kennel Club Genetics Centre, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk, United Kingdom.
    Narfström, Kristina
    Section for Comparative Ophthalmology, College of Veterinary Medicine, University of Missouri-Columbia, Missouri, United States of America.
    Hallböök, Finn
    Department of Neuroscience, Uppsala University, Uppsala, Sweden.
    Ekesten, Björn
    Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Andersson, Göran
    Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Bergström, Tomas F
    Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    An ABCA4 loss-of-function mutation causes a canine form of Stargardt disease2019In: PLoS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 15, no 3, article id e1007873Article in journal (Refereed)
    Abstract [en]

    Autosomal recessive retinal degenerative diseases cause visual impairment and blindness in both humans and dogs. Currently, no standard treatment is available, but pioneering gene therapy-based canine models have been instrumental for clinical trials in humans. To study a novel form of retinal degeneration in Labrador retriever dogs with clinical signs indicating cone and rod degeneration, we used whole-genome sequencing of an affected sib-pair and their unaffected parents. A frameshift insertion in the ATP binding cassette subfamily A member 4 (ABCA4) gene (c.4176insC), leading to a premature stop codon in exon 28 (p.F1393Lfs*1395), was identified. In contrast to unaffected dogs, no full-length ABCA4 protein was detected in the retina of an affected dog. The ABCA4 gene encodes a membrane transporter protein localized in the outer segments of rod and cone photoreceptors. In humans, the ABCA4 gene is associated with Stargardt disease (STGD), an autosomal recessive retinal degeneration leading to central visual impairment. A hallmark of STGD is the accumulation of lipofuscin deposits in the retinal pigment epithelium (RPE). The discovery of a canine homozygous ABCA4 loss-of-function mutation may advance the development of dog as a large animal model for human STGD.

  • 23.
    Riddell, Nicole
    et al.
    Wellington Laboratories Inc., Guelph ON, Canada; Man-Technology-Environment (MTM) Research Center, Örebro University, Örebro, Sweden.
    van Bavel, Bert
    Örebro University, School of Science and Technology. Norwegian Institute for Water Research, Oslo, Norway.
    Ericson Jogsten, Ingrid
    Örebro University, School of Science and Technology.
    McCrindle, Robert
    Chemistry Department, University of Guelph, Guelph, Canada.
    McAlees, Alan
    Wellington Laboratories Inc., Guelph ON, Canada.
    Chittim, Brock
    Wellington Laboratories Inc., Guelph ON, Canada.
    Coupling supercritical fluid chromatography to positive ion atmospheric pressure ionization mass spectrometry: Ionization optimization of halogenated environmental contaminants2017In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 421, p. 156-163Article in journal (Refereed)
    Abstract [en]

    Currently used analytical techniques for halogenated aromatic environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs), also known as legacy persistent organic pollutants, are based on gas chromatographic separation of target analytes and detection by mass spectrometry. The coupling of packed column supercritical fluid chromatography (SFC) to atmospheric pressure ionization mass spectrometry (API/MS) could allow for the concurrent analysis of thermally labile and legacy halogenated environmental contaminants if ionization can be sufficiently optimized. The evaluation of positive ion atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) as well as possible charge transfer dopants for the generation of molecular ion isotopomeric clusters of halogenated environmental contaminants with minimal fragmentation has been completed. Using the investigated parameters, positive ion APPI was found to be the more sensitive technique. Of the aromatic and cycloalkane dopants investigated, only fluorobenzene and trifluorotoluene were found to be effective dopants for the halogenated aromatic target analytes (PCDDs, PCDFs, and PCBs). Experiments involving deuterated dopants confirmed that reactive species generated by cycloalkanes were quenched by the SFC eluent rendering them unusable in conjunction with the investigated separation technique. Alternatively, aromatic dopants were found to be less susceptible to quenching by the SFC eluent and fluorobenzene was determined to be the most effective charge transfer dopant for PCDDs, PCDFs, and PCBs. To demonstrate the applicability of the optimized ionization conditions, SFC-API/MS has been used for the concurrent analysis of legacy halogenated aromatic environmental contaminants (PCDDs, PCDFs, and PCBs) and thermally labile analytes (alpha, beta, and gamma isomers of hexabromocyclododecane).

  • 24.
    Roussou, Alexandra
    et al.
    Department of Applied Mathematics, University of Crete, Heraklion, Greece.
    Smyrnakis, Ioannis
    Technological Education Institute of Crete, Heraklion, Greece.
    Magiropoulos, Manolis
    Technological Education Institute of Crete, Heraklion, Greece.
    Efremidis, Nikolaos
    Department of Applied Mathematics, University of Crete, Heraklion, Greece.
    Kavoulakis, Georgios
    Technological Education Institute of Crete, Heraklion, Greece.
    Sandin, Patrik
    Örebro University, School of Science and Technology.
    Ögren, Magnus
    Örebro University, School of Science and Technology.
    Gulliksson, Mårten
    Örebro University, School of Science and Technology.
    Excitation spectrum of a mixture of two Bose gases confined in a ring potential with interaction asymmetry2018In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 20, article id 045006Article in journal (Refereed)
    Abstract [en]

    We study the rotational properties of a two-component Bose-Einstein condensed gas of distinguishable atoms which are confined in a ring potential using both the mean-field approximation, as well as the method of diagonalization of the many-body Hamiltonian. We demonstrate that the angular momentum may be given to the system either via single-particle, or "collective" excitation. Furthermore, despite the complexity of this problem, under rather typical conditions the dispersion relation takes a remarkably simple and regular form. Finally, we argue that under certain conditions the dispersion relation is determined via collective excitation. The corresponding many-body state, which, in addition to the interaction energy minimizes also the kinetic energy, is dictated by elementary number theory.

  • 25.
    Tjörnhammar, Staffan
    et al.
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Eklöf, Finn Klemming
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Yu, Zhangwei
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Hällstig, Emil
    Fotonic, Stockholm, Sweden .
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Laurell, Fredrik
    Department of Applied Physics, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Multiwavelength laser designed for single-frame digital holography2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 27, p. 7517-7521Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a tailored multiwavelength Yb-fiber laser source in the 1.03 μm spectral region for spatially multiplexed digital holographic acquisitions. The wavelengths with bandwidths below 0.1 nm were spectrally separated by approximately 1 nm by employing fiber Bragg gratings for spectral control. As a proof of concept, the shape of a cylindrically shaped object with a diameter of 48 mm was measured. The holographic acquisition was performed in single-shot dual-wavelength mode with a synthetic wavelength of 1.1 mm, and the accuracy was estimated to be 3% of the synthetic wavelength.

  • 26.
    Yu, Y.
    et al.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Ögren, Magnus
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Åberg, S.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Reimann, S. M.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Brack, M.
    Institut für Theoretische Physik, Universität Regensburg, Regensburg, Germany.
    Supershell structure in trapped dilute Fermi gases2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 72, no 5, article id 051602Article in journal (Refereed)
    Abstract [en]

    We show that a dilute harmonically trapped two-component gas of fermionic atoms with a weak repulsive interaction has a pronounced super-shell structure: The shell fillings due to the spherical harmonic trapping potential are modulated by a beat mode. This changes the "magic numbers" occurring between the beat nodes by half a period. The length and amplitude of this beating mode depend on the strength of the interaction. We give a simple interpretation of the beat structure in terms of a semiclassical trace formula for the symmetry breaking U(3)→SO(3).

  • 27.
    Ögren, Magnus
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Klassisk mekanik vs kvantmekanik2010In: Forskning, ISSN 1654-8876, no 3-4, p. 50-54Article, review/survey (Other (popular science, discussion, etc.))
  • 28.
    Ögren, Magnus
    et al.
    Örebro University, School of Science and Technology.
    Abdullaev, Fatkhulla
    Physical-Technical Institute, Uzbekistan Academy of Sciences, Tashkent, Uzbekistan .
    Konotop, Vladimir
    Centro de Física Teórica e Computacional and Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal .
    Solitons in a 𝒫𝒯-symmetric 𝜒(2) coupler2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 20, p. 4079-4082Article in journal (Refereed)
    Abstract [en]

    We consider the existence and stability of solitons in a 𝜒(2) coupler. Both the fundamental and second harmonics (SHs) undergo gain in one of the coupler cores and are absorbed in the other one. The gain and loss are balanced, creating a parity-time (𝒫𝒯) symmetric configuration. We present two types of families of 𝒫𝒯-symmetric solitons having equal and different profiles of the fundamental and SHs. It is shown that the gain and loss can stabilize solitons. The interaction of stable solitons is shown. In the cascading limit, the model is reduced to the 𝒫𝒯-symmetric coupler with effective Kerr-type nonlinearity and the balanced nonlinear gain and loss.

  • 29.
    Ögren, Magnus
    et al.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Heiselberg, H.
    University of Southern Denmark, Odense, Denmark.
    Supershell structures and pairing in ultracold trapped Fermi gases2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 2, article id 021601Article in journal (Refereed)
    Abstract [en]

    We calculate level densities and pairing gaps for an ultracold dilute gas of fermionic atoms in harmonic traps under the influence of mean field and anharmonic quartic trap potentials. Supershell nodes, which were found in Hartree-Fock calculations, are calculated analytically within periodic orbit theory as well as from WKB calculations. For attractive interactions, the underlying level densities are crucial for pairing and supershell structures in gaps are predicted.

  • 30.
    Ögren, Magnus
    et al.
    Department of Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Kavoulakis, G. M.
    Department of Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Persistent currents in a Bose-Einstein condensate in the presence of disorder2007In: Journal of Low Temperature Physics, ISSN 0022-2291, E-ISSN 1573-7357, Vol. 149, no 3-4, p. 176-184Article in journal (Refereed)
    Abstract [en]

    We examine bosonic atoms that are confined in a toroidal, quasi-one-dimensional trap, subjected to a random potential. The resulting inhomogeneous atomic density is smoothened for sufficiently strong, repulsive interatomic interactions. Statistical analysis of our simulations show that the gas supports persistent currents, which become more fragile due to the disorder.

  • 31.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia; Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Kavoulakis, G. M.
    Technological Education Institute of Crete, Heraklion, Greece.
    Stability of persistent currents in a Bose-Einstein condensate confined in a toroidal trap2009In: Journal of Low Temperature Physics, ISSN 0022-2291, E-ISSN 1573-7357, Vol. 154, no 1-2, p. 30-40Article in journal (Refereed)
    Abstract [en]

    Motivated by recent experiments in Bose-Einstein condensed atoms that have been confined in toroidal traps, we examine the stability of persistent currents in such systems. We investigate the extent that the stability of these currents may be tunable, and the possible difficulties in their creation and detection.

  • 32.
    Ögren, Magnus
    et al.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Kavoulakis, G. M.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Jackson, A. D.
    Niels Bohr Institute, Copenhagen, Denmark.
    Solitary waves in elongated clouds of strongly interacting bosons2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 72, no 2, article id 021603Article in journal (Refereed)
    Abstract [en]

    We examine the propagation of solitary waves in elongated clouds of trapped bosonic atoms as the confinement, the strength of the interatomic interaction, and the atom density are varied. We identify three different physical regimes and develop a general formalism that allows us to interpolate between them. Finally we pay special attention to the transition to the Tonks-Girardeau limit of strongly interacting bosons.

  • 33.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia.
    Kheruntsyan, K. V.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia.
    Atom-atom correlations and relative number squeezing in dissociation of spatially inhomogeneous molecular condensates2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 78, no 1, article id 011602Article in journal (Refereed)
    Abstract [en]

    We study atom-atom correlations and relative number squeezing in the dissociation of a Bose-Einstein condensate (BEC) of molecular dimers made of either bosonic or fermionic atom pairs. Our treatment addresses the role of the spatial inhomogeneity of the molecular BEC on the strength of correlations in the short time limit. We obtain explicit analytic results for the density-density correlation functions in momentum space, and show that the correlation widths and the degree of relative number squeezing are determined merely by the shape of the molecular condensate.

  • 34.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia.
    Kheruntsyan, K. V.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia.
    Atom-atom correlations in colliding Bose-Einstein condensates2009In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 79, no 2, article id 021606Article in journal (Refereed)
    Abstract [en]

    We analyze atom-atom correlations in the s -wave scattering halo of two colliding condensates. By developing a simple perturbative approach, we obtain explicit analytic results for the collinear (CL) and back-to-back (BB) correlations corresponding to realistic density profiles of the colliding condensates with interactions. The results in the short-time limit are in agreement with the first-principles simulations using the positive- P representation and provide analytic insights into the experimental observations of Perrin [Phys. Rev. Lett. 99, 150405 (2007)]. For long collision durations, we predict that the BB correlation becomes broader than the CL correlation.

  • 35.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Kheruntsyan, K. V.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Role of spatial inhomogeneity in dissociation of trapped molecular condensates2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 1, article id 013641Article in journal (Refereed)
    Abstract [en]

    We theoretically analyze dissociation of a harmonically trapped Bose-Einstein condensate of molecular dimers and examine how the spatial inhomogeneity of the molecular condensate affects the conversion dynamics and the atom-atom pair correlations in the short-time limit. Both fermionic and bosonic statistics of the constituent atoms are considered. Using the undepleted molecular-field approximation, we obtain explicit analytic results for the asymptotic behavior of the second-order correlation functions and for the relative number squeezing between the dissociated atoms in one, two, and three spatial dimensions. Comparison with the numerical results shows that the analytic approach employed here captures the main underlying physics and provides useful insights into the dynamics of dissociation for conversion efficiencies up to 10%. The results show explicitly how the strength of atom-atom correlations and relative number squeezing degrade with the reduction of the size of the molecular condensate.

  • 36.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Kheruntsyan, K. V.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Corney, J. F.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    First-principles quantum dynamics for fermions: Application to molecular dissociation2010In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 92, no 3, article id 36003Article in journal (Refereed)
    Abstract [en]

    We demonstrate that the quantum dynamics of a many-body Fermi-Bose system can be simulated using a Gaussian phase-space representation method. In particular, we consider the application of the mixed fermion-boson model to ultracold quantum gases and simulate the dynamics of dissociation of a Bose-Einstein condensate of bosonic dimers into pairs of fermionic atoms. We quantify deviations of atom-atom pair correlations from Wick's factorization scheme, and show that atom-molecule and molecule-molecule correlations grow with time, in clear departures from pairing mean-field theories. As a first-principles approach, the method provides benchmarking of approximate approaches and can be used to validate dynamical probes for characterizing strongly correlated phases of fermionic systems.

  • 37.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Kheruntsyan, K. V.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Corney, J. F.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Stochastic simulations of fermionic dynamics with phase-space representations2011In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 182, no 9, p. 1999-2003Article in journal (Refereed)
    Abstract [en]

    A Gaussian operator basis provides a means to formulate phase-space simulations of the real- and imaginary-time evolution of quantum systems. Such simulations are guaranteed to be exact while the underlying distribution remains well-bounded, which defines a useful simulation time. We analyse the application of the Gaussian phase-space representation to the dynamics of the dissociation of an ultra-cold molecular gas. We show how the choice of mapping to stochastic differential equations can be used to tailor the stochastic behaviour, and thus the useful simulation time. In the phase-space approach, it is only averages of stochastic trajectories that have a direct physical meaning. Whether particular constants of the motion are satisfied by individual trajectories depends on the choice of mapping, as we show in examples.

  • 38.
    Ögren, Magnus
    et al.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Kärkkäinen, K.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Yu, Y.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Reimann, S. M.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    On the spin asymmetry of ground states in trapped two-component Fermi gases with repulsive interactions2007In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, no 13, p. 2653-2660Article in journal (Refereed)
    Abstract [en]

    We examine the spin asymmetry of ground states for two-dimensional, harmonically trapped two-component gases of fermionic atoms at zero temperature with weakly repulsive short-range interactions. Our main result is that, in contrast to the three-dimensional case, in two dimensions a non-trivial spin-asymmetric phase can only be caused by the shell structure. A simple, qualitative description is given in terms of an approximate single-particle model, comparing well to the standard results of Hartree-Fock or direct diagonalization methods.

  • 39.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia.
    Savage, C. M.
    Department of Quantum Science, ARC Centre of Excellence for Quantum-Atom Optics, Australian National University, Canberra, Australia.
    Kheruntsyan, K. V.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Australia.
    Directional effects due to quantum statistics in dissociation of elongated molecular condensates2009In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 79, no 4, article id 043624Article in journal (Refereed)
    Abstract [en]

    Ultracold clouds of dimeric molecules can dissociate into quantum mechanically correlated constituent atoms that are either both bosons or both fermions. We theoretically model the dissociation of two-dimensional anisotropic molecular condensates for which this difference manifests as complementary geometric structures of the dissociated atoms. Atomic bosons are preferentially emitted along the long axis of the molecular condensate, while atomic fermions are preferentially emitted along the short axis. This anisotropy potentially simplifies the measurement of correlations between the atoms through relative number squeezing.

  • 40.
    Ögren, Magnus
    et al.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Yu, Y.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Åberg, S.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Reimann, S. M.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Brack, M.
    Institut für Theoretische Physik, Universität Regensburg, Regensburg, Germany.
    Super-shell structure in harmonically trapped fermionic gases and its semi-classical interpretation2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, no T125, p. 37-40Article in journal (Refereed)
    Abstract [en]

    It was recently shown in self-consistent Hartree–Fock calculations that a harmonically trapped dilute gas of fermionic atoms with a repulsive two-body interaction exhibits a pronounced super-shell structure: the shell fillings due to the spherical harmonic trapping potential are modulated by a beat mode. This changes the 'magic numbers' occurring between the beat nodes by half a period. The length and amplitude of the beating mode depends on the strength of the interaction. We give a qualitative interpretation of the beat structure in terms of a semi-classical trace formula that uniformly describes the symmetry breaking U(3) → SO(3) in a three-dimensional harmonic oscillator potential perturbed by an anharmonic term ∝ r 4 with arbitrary strength. We show that at low Fermi energies (or particle numbers), the beating gross-shell structure of this system is dominated solely by the twofold degenerate circular and (diametrically) pendulating orbits.

1 - 40 of 40
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