39 results found
Mingarelli L, Keaveny EE, Barnett R, 2018, Vortex lattices in binary mixtures of repulsive superfluids, Physical Review A, Vol: 97, ISSN: 2469-9926
© 2018 American Physical Society. We present an extension of the framework introduced in previous work [L. Mingarelli, E. E. Keaveny, and R. Barnett, J. Phys.: Condens. Matter 28, 285201 (2016)JCOMEL0953-898410.1088/0953-8984/28/28/285201] to treat multicomponent systems, showing that new degrees of freedom are necessary in order to obtain the desired boundary conditions. We then apply this extended framework to the coupled Gross-Pitaevskii equations to investigate the ground states of two-component systems with equal masses, thereby extending previous work in the lowest Landau limit [E. J. Mueller and T.-L. Ho, Phys. Rev. Lett. 88, 180403 (2002)PRLTAO0031-900710.1103/PhysRevLett.88.180403] to arbitrary interactions within Gross-Pitaevskii theory. We show that away from the lowest Landau level limit, the predominant vortex lattice consists of two interlaced triangular lattices. Finally, we derive a linear relation which accurately describes the phase boundaries in the strong interacting regimes.
Wrubel JP, Schwettmann A, Fahey DP, et al., 2018, Spinor Bose-Einstein-condensate phase-sensitive amplifier for SU(1,1) interferometry
© 2018 American Physical Society. US. The SU(1,1) interferometer was originally conceived as a Mach-Zehnder interferometer with the beam splitters replaced by parametric amplifiers. The parametric amplifiers produce states with correlations that result in enhanced phase sensitivity. F=1 spinor Bose-Einstein condensates (BECs) can serve as the parametric amplifiers for an atomic version of such an interferometer by collisionally producing entangled pairs of |F=1,m=±1) atoms. We simulate the effect of single- and double-sided seeding of the inputs to the amplifier using the truncated-Wigner approximation. We find that single-sided seeding degrades the performance of the interferometer exactly at the phase the unseeded interferometer should operate the best. Double-sided seeding results in a phase-sensitive amplifier, where the maximal sensitivity is a function of the phase relationship between the input states of the amplifier. In both single- and double-sided seeding we find there exists an optimal phase shift that achieves sensitivity beyond the standard quantum limit. Experimentally, we demonstrate a spinor phase-sensitive amplifier using a BEC of Na23 in an optical dipole trap. This configuration could be used as an input to such an interferometer. We are able to control the initial phase of the double-seeded amplifier and demonstrate sensitivity to initial population fractions as small as 0.1%.
Galilo B, Lee DKK, Barnett R, 2017, Topological Edge-State Manifestation of Interacting 2D Condensed Boson-Lattice Systems in a Harmonic Trap, PHYSICAL REVIEW LETTERS, Vol: 119, ISSN: 0031-9007
Jevtic S, Barnett R, 2017, Frustration-free Hamiltonians supporting Majorana zero edge modes, New Journal of Physics, Vol: 19, ISSN: 1367-2630
© 2017 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. A one-dimensional fermionic system, such as a superconducting wire, may host Majorana zero-energy edge modes (MZMs) at its edges when it is in the topological phase. MZMs provide a path to realising fault-tolerant quantum computation, and so are the focus of intense experimental and theoretical studies. However, given a Hamiltonian, determining whether MZMs exist is a daunting task as it relies on knowing the spectral properties of the Hamiltonian in the thermodynamic limit. The Kitaev chain is a paradigmatic non-interacting model that supports MZMs and the Hamiltonian can be fully diagonalised. However, for interacting models, the situation is far more complex. Here we consider a different classification of models, namely, ones with frustration-free Hamiltonians. Within this class of models, interacting and non-interacting systems are treated on an equal footing, and we identify exactly which Hamiltonians can realise MZMs.
Mingarelli L, Keaveny EE, Barnett R, 2016, Simulating infinite vortex lattices in superfluids, Journal of Physics Condensed Matter, Vol: 28, ISSN: 0953-8984
© 2016 IOP Publishing Ltd. We present an efficient framework to numerically treat infinite periodic vortex lattices in rotating superfluids described by the Gross-Pitaevskii theory. The commonly used split-step Fourier (SSF) spectral methods are inapplicable to such systems as the standard Fourier transform does not respect the boundary conditions mandated by the magnetic translation group. We present a generalisation of the SSF method which incorporates the correct boundary conditions by employing the so-called magnetic Fourier transform. We test the method and show that it reduces to known results in the lowest-Landau-level regime. While we focus on rotating scalar superfluids for simplicity, the framework can be naturally extended to treat multicomponent systems and systems under more general 'synthetic' gauge fields.
Payrits M, Barnett R, 2016, Quantum rotor theory of systems of spin-2 bosons, Physical Review A, Vol: 94, ISSN: 2469-9926
© 2016 American Physical Society. We consider quantum phases of tightly confined spin-2 bosons in an external field under the presence of rotationally invariant interactions. Generalizing previous treatments, we show how this system can be mapped onto a quantum rotor model. Within the rotor framework, low-energy excitations about fragmented states, which cannot be accessed within standard Bogoliubov theory, can be obtained. In the spatially extended system in the thermodynamic limit there exists a mean field ground-state degeneracy between a family of nematic states for appropriate interaction parameters. It has been established that quantum fluctuations lift this degeneracy through the mechanism of order by disorder and select either a uniaxial or square-biaxial ground state. On the other hand, in the full quantum treatment of the analogous single-spatial-mode problem with finite-particle number, it is known that, due to symmetry-restoring fluctuations, there is a unique ground state across the entire nematic region of the phase diagram. Within the established rotor framework, we investigate the possible quantum phases under the presence of a quadratic Zeeman field, a problem which has previously received little attention. By investigating wave-function overlaps, we do not find any signatures of the order-by-disorder phenomenon which is present in the continuum case. Motivated by this, we consider an alternative external potential which breaks less symmetry than the quadratic Zeeman field. For this case, we do find the phenomenon of order by disorder in the fully quantum system. This is established within the rotor framework and with exact diagonalization.
Galilo B, Lee DKK, Barnett R, 2015, Selective Population of Edge States in a 2D Topological Band System, PHYSICAL REVIEW LETTERS, Vol: 115, ISSN: 0031-9007
Payrits M, Barnett R, 2014, Order-by-disorder degeneracy lifting of interacting bosons on the dice lattice, PHYSICAL REVIEW A, Vol: 90, ISSN: 1050-2947
Barnett R, 2013, Edge-state instabilities of bosons in a topological band, PHYSICAL REVIEW A, Vol: 88, ISSN: 1050-2947
Pechkis HK, Wrubel JP, Schwettmann A, et al., 2013, Spinor Dynamics in an Antiferromagnetic Spin-1 Thermal Bose Gas, PHYSICAL REVIEW LETTERS, Vol: 111, ISSN: 0031-9007
Barnett R, Boyd GR, Galitski V, 2012, SU(3) Spin-Orbit Coupling in Systems of Ultracold Atoms, PHYSICAL REVIEW LETTERS, Vol: 109, ISSN: 0031-9007
Barnett R, Powell S, Grass T, et al., 2012, Order by disorder in spin-orbit-coupled Bose-Einstein condensates, PHYSICAL REVIEW A, Vol: 85, ISSN: 1050-2947
Barnett R, Powell S, Graß T, et al., 2012, Erratum: Order by disorder in spin-orbit-coupled Bose-Einstein condensates (Physical Review A - Atomic, Molecular, and Optical Physics), Physical Review A - Atomic, Molecular, and Optical Physics, Vol: 85, ISSN: 1050-2947
Hui H-Y, Barnett R, Porto JV, et al., 2012, Loop-structure stability of a double-well-lattice Bose-Einstein condensate, PHYSICAL REVIEW A, Vol: 86, ISSN: 1050-2947
Barnett R, Hui H-Y, Lin C-H, et al., 2011, Quantum rotor theory of spinor condensates in tight traps, PHYSICAL REVIEW A, Vol: 83, ISSN: 1050-2947
Barnett R, Polkovnikov A, Vengalattore M, 2011, Prethermalization in quenched spinor condensates, PHYSICAL REVIEW A, Vol: 84, ISSN: 2469-9926
Hui H-Y, Barnett R, Sensarma R, et al., 2011, Instabilities of bosonic spin currents in optical lattices, PHYSICAL REVIEW A, Vol: 84, ISSN: 2469-9926
Powell S, Barnett R, Sensarma R, et al., 2011, Bogoliubov theory of interacting bosons on a lattice in a synthetic magnetic field, PHYSICAL REVIEW A, Vol: 83, ISSN: 2469-9926
Barnett R, Chen E, Refael G, 2010, Vortex synchronization in Bose-Einstein condensates: a time-dependent Gross-Pitaevskii equation approach, NEW JOURNAL OF PHYSICS, Vol: 12, ISSN: 1367-2630
Barnett R, Sau JD, Das Sarma S, 2010, Antiferromagnetic spinor condensates are quantum rotors, PHYSICAL REVIEW A, Vol: 82, ISSN: 1050-2947
Powell S, Barnett R, Sensarma R, et al., 2010, Interacting Hofstadter Spectrum of Atoms in an Artificial Gauge Field, PHYSICAL REVIEW LETTERS, Vol: 104, ISSN: 0031-9007
Zou Y, Barnett R, Refael G, 2010, Particle-hole symmetric localization in optical lattices using time modulated random on-site potentials, PHYSICAL REVIEW B, Vol: 82, ISSN: 1098-0121
Barnett R, Podolsky D, Refael G, 2009, Geometrical approach to hydrodynamics and low-energy excitations of spinor condensates, PHYSICAL REVIEW B, Vol: 80, ISSN: 2469-9950
Barnett R, Mukerjee S, Moore JE, 2008, Vortex lattice transitions in cyclic spinor condensates, PHYSICAL REVIEW LETTERS, Vol: 100, ISSN: 0031-9007
Barnett R, Refael G, Porter MA, et al., 2008, Vortex lattice locking in rotating two-component Bose-Einstein condensates, NEW JOURNAL OF PHYSICS, Vol: 10, ISSN: 1367-2630
Barnett R, Turner A, Demler E, 2007, Classifying vortices in S=3 Bose-Einstein condensates, PHYSICAL REVIEW A, Vol: 76, ISSN: 2469-9926
Barnett RL, Maragakis P, Turner A, et al., 2007, Multiscale model of electronic behavior and localization in stretched dry DNA, JOURNAL OF MATERIALS SCIENCE, Vol: 42, Pages: 8894-8903, ISSN: 0022-2461
Turner AM, Barnett R, Demler E, et al., 2007, Nematic order by disorder in spin-2 Bose-Einstein condensates, PHYSICAL REVIEW LETTERS, Vol: 98, ISSN: 0031-9007
Barnett R, Petrov D, Lukin M, et al., 2006, Quantum magnetism with multicomponent dipolar molecules in an optical lattice, PHYSICAL REVIEW LETTERS, Vol: 96, ISSN: 0031-9007
Barnett R, Turner A, Demler E, 2006, Classifying novel phases of spinor atoms, PHYSICAL REVIEW LETTERS, Vol: 97, ISSN: 0031-9007
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