1103.0557 (Lea F. Santos et al.)

Entropy of isolated quantum systems after a quench    [PDF]

Lea F. Santos, Anatoli Polkovnikov, Marcos Rigol

A diagonal entropy, which depends only on the diagonal elements of the
system's density matrix in the energy representation, has been recently
introduced as the proper definition of thermodynamic entropy in
out-of-equilibrium quantum systems. We study this quantity after an interaction
quench in lattice hard-core bosons and spinless fermions, and after a local
chemical potential quench in a system of hard-core bosons in a superlattice
potential. The former systems have a chaotic regime, where the diagonal entropy
becomes equivalent to the equilibrium microcanonical entropy, coinciding with
the onset of thermalization. The latter system is integrable. We show that its
diagonal entropy is additive and different from the entropy of a generalized
Gibbs ensemble, which has been introduced to account for the effects of
conserved quantities at integrability.

View original: http://arxiv.org/abs/1103.0557