Imperial College London

DrRyanBarnett

Faculty of Natural SciencesDepartment of Mathematics

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 8536r.barnett Website

 
 
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Location

 

6M49Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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37 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.

JOURNAL ARTICLE

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

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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.

JOURNAL ARTICLE

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.

JOURNAL ARTICLE

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.

JOURNAL ARTICLE

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

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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

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Barnett R, 2013, Edge-state instabilities of bosons in a topological band, PHYSICAL REVIEW A, Vol: 88, ISSN: 1050-2947

JOURNAL ARTICLE

Pechkis HK, Wrubel JP, Schwettmann A, Griffin PF, Barnett R, Tiesinga E, Lett PDet al., 2013, Spinor Dynamics in an Antiferromagnetic Spin-1 Thermal Bose Gas, PHYSICAL REVIEW LETTERS, Vol: 111, ISSN: 0031-9007

JOURNAL ARTICLE

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

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Barnett R, Powell S, Grass T, Lewenstein M, Das Sarma Set al., 2012, Order by disorder in spin-orbit-coupled Bose-Einstein condensates, PHYSICAL REVIEW A, Vol: 85, ISSN: 1050-2947

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Barnett R, Powell S, GraƟ T, Lewenstein M, Das Sarma Set 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

JOURNAL ARTICLE

Hui H-Y, Barnett R, Porto JV, Das Sarma Set al., 2012, Loop-structure stability of a double-well-lattice Bose-Einstein condensate, PHYSICAL REVIEW A, Vol: 86, ISSN: 1050-2947

JOURNAL ARTICLE

Barnett R, Hui H-Y, Lin C-H, Sau JD, Das Sarma Set al., 2011, Quantum rotor theory of spinor condensates in tight traps, PHYSICAL REVIEW A, Vol: 83, ISSN: 1050-2947

JOURNAL ARTICLE

Barnett R, Polkovnikov A, Vengalattore M, 2011, Prethermalization in quenched spinor condensates, PHYSICAL REVIEW A, Vol: 84, ISSN: 2469-9926

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Hui H-Y, Barnett R, Sensarma R, Das Sarma Set al., 2011, Instabilities of bosonic spin currents in optical lattices, PHYSICAL REVIEW A, Vol: 84, ISSN: 2469-9926

JOURNAL ARTICLE

Powell S, Barnett R, Sensarma R, Das Sarma Set al., 2011, Bogoliubov theory of interacting bosons on a lattice in a synthetic magnetic field, PHYSICAL REVIEW A, Vol: 83, ISSN: 2469-9926

JOURNAL ARTICLE

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

JOURNAL ARTICLE

Barnett R, Sau JD, Das Sarma S, 2010, Antiferromagnetic spinor condensates are quantum rotors, PHYSICAL REVIEW A, Vol: 82, ISSN: 1050-2947

JOURNAL ARTICLE

Powell S, Barnett R, Sensarma R, Das Sarma Set al., 2010, Interacting Hofstadter Spectrum of Atoms in an Artificial Gauge Field, PHYSICAL REVIEW LETTERS, Vol: 104, ISSN: 0031-9007

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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

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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

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Barnett R, Mukerjee S, Moore JE, 2008, Vortex lattice transitions in cyclic spinor condensates, PHYSICAL REVIEW LETTERS, Vol: 100, ISSN: 0031-9007

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Barnett R, Refael G, Porter MA, Buechler HPet al., 2008, Vortex lattice locking in rotating two-component Bose-Einstein condensates, NEW JOURNAL OF PHYSICS, Vol: 10, ISSN: 1367-2630

JOURNAL ARTICLE

Barnett R, Turner A, Demler E, 2007, Classifying vortices in S=3 Bose-Einstein condensates, PHYSICAL REVIEW A, Vol: 76, ISSN: 2469-9926

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Barnett RL, Maragakis P, Turner A, Fyta M, Kaxiras Eet 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

JOURNAL ARTICLE

Turner AM, Barnett R, Demler E, Vishwanath Aet al., 2007, Nematic order by disorder in spin-2 Bose-Einstein condensates, PHYSICAL REVIEW LETTERS, Vol: 98, ISSN: 0031-9007

JOURNAL ARTICLE

Barnett R, Petrov D, Lukin M, Demler Eet al., 2006, Quantum magnetism with multicomponent dipolar molecules in an optical lattice, PHYSICAL REVIEW LETTERS, Vol: 96, ISSN: 0031-9007

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Barnett R, Turner A, Demler E, 2006, Classifying novel phases of spinor atoms, PHYSICAL REVIEW LETTERS, Vol: 97, ISSN: 0031-9007

JOURNAL ARTICLE

Barnett RL, Polkovnikov A, Demler E, Yin WG, Ku Wet al., 2006, Coexistence of gapless excitations and commensurate charge-density wave in the 2H transition metal dichalcogenides, PHYSICAL REVIEW LETTERS, Vol: 96, ISSN: 0031-9007

JOURNAL ARTICLE

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