Discrete breathers and negative-temperature states

Year: 2013

Authors: Iubini S., Franzosi R., Livi R., Oppo G.-L., Politi A.

Autors Affiliation: Dipartimento di Fisica e Astronomia—CSDC, Università di Firenze and INFN Sezione di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino, Italy; CNR—Istituto dei Sistemi Complessi, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy; ICS, SUPA and Department of Physics, University of Strathclyde,107 Rottenrow, Glasgow G4 ONG, UK; ICSMB, SUPA and Department of Physics, University of Aberdeen, Aberdeen AB24 3UE, UK; QSTAR, Largo Enrico Fermi 2, I-50125 Firenze, Italy

Abstract: We explore the statistical behaviour of the discrete nonlinear Schrodinger equation as a test bed for the observation of negative-temperature (i.e. above infinite temperature) states in Bose-Einstein condensates in optical lattices and arrays of optical waveguides. By monitoring the microcanonical temperature, we show that there exists a parameter region where the system evolves towards a state characterized by a finite density of discrete breathers and a negative temperature. Such a state persists over very long (astronomical) times since the convergence to equilibrium becomes increasingly slower as a consequence of a coarsening process. We also discuss two possible mechanisms for the generation of negative-temperature states in experimental setups, namely, the introduction of boundary dissipations and the free expansion of wavepackets initially in equilibrium at a positive temperature.

Journal/Review: NEW JOURNAL OF PHYSICS

Volume: 15      Pages from: 023032  to: 023032

More Information: RL acknowledges financial support from the Italian MIUR-PRIN project no. 20083C8XFZ and G-LO from the EU Commission FET Open Grant HIDEAS. We acknowledge financial support from EPSRC grant EP/I006826/1. SI and AP thank T Carletti for useful discussions on the implementation of symplectic integrators.
KeyWords: Bose-Einstein condensates; Boundary dissipations; Coarsening process; Convergence to equilibrium; Dinger equation; Discrete breather; Finite density; Microcanonical temperature; Negative temperatures; Parameter regions; Possible mechanisms, Bose-Einstein condensation; Equipment testing, Nonlinear equations
DOI: 10.1088/1367-2630/15/2/023032

Citations: 40
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