Threshold coupling strength for equilibration between small systems
Abstract
In this paper we study the thermal equilibration of small bipartite BoseHubbard systems, both quantum mechanically and in meanfield approximation. In particular we consider small systems composed of a singlemode "thermometer" coupled to a threemode "bath," with no additional environment acting on the fourmode system, and test the hypothesis that the thermometer will thermalize if and only if the bath is chaotic. We find that chaos in the bath alone is neither necessary nor sufficient for equilibration in these isolated fourmode systems. The two subsystems can thermalize if the combined system is chaotic even when neither subsystem is chaotic in isolation, and under full quantum dynamics there is a minimum coupling strength between the thermometer and the bath below which the system does not thermalize even if the bath itself is chaotic. We show that the quantum coupling threshold scales like 1 /N (where N is the total particle number), so that the classical results are obtained in the limit N →∞ .
 Publication:

Physical Review A
 Pub Date:
 June 2019
 DOI:
 10.1103/PhysRevA.99.063617
 arXiv:
 arXiv:1903.12083
 Bibcode:
 2019PhRvA..99f3617B
 Keywords:

 Quantum Physics
 EPrint:
 Phys. Rev. A 99, 063617 (2019)