"Light-cone" dynamics after quantum quenches in spin chains.
Physical review letters 113:18 (2014) 187203
Abstract:
Signal propagation in the nonequilibrium evolution after quantum quenches has recently attracted much experimental and theoretical interest. A key question arising in this context is what principles, and which of the properties of the quench, determine the characteristic propagation velocity. Here we investigate such issues for a class of quench protocols in one of the central paradigms of interacting many-particle quantum systems, the spin-1/2 Heisenberg XXZ chain. We consider quenches from a variety of initial thermal density matrices to the same final Hamiltonian using matrix product state methods. The spreading velocities are observed to vary substantially with the initial density matrix. However, we achieve a striking data collapse when the spreading velocity is considered to be a function of the excess energy. Using the fact that the XXZ chain is integrable, we present an explanation of the observed velocities in terms of "excitations" in an appropriately defined generalized Gibbs ensemble.Entanglement entropies of the quarter filled Hubbard model
Journal of Statistical Mechanics Theory and Experiment IOP Publishing 2014:9 (2014) p09025
Quench Dynamics in a Model with Tuneable Integrability Breaking
Physical Review B American Physical Society 89:16 (2014) 165104
Abstract:
We consider quantum quenches in an integrable quantum chain with tuneable-integrability-breaking interactions. In the case where these interactions are weak, we demonstrate that at intermediate times after the quench local observables relax to a prethermalized regime, which can be described by a density matrix that can be viewed as a deformation of a generalized Gibbs ensemble. We present explicit expressions for the approximately conserved charges characterizing this ensemble. We do not find evidence for a crossover from the prethermalized to a thermalized regime on the time scales accessible to us. Increasing the integrability-breaking interactions leads to a behaviour that is compatible with eventual thermalization.Relaxation after quantum quenches in the spin-12 Heisenberg XXZ chain
Physical Review B American Physical Society (APS) 89:12 (2014) 125101
Time evolution of local observables after quenching to an integrable model
Physical Review Letters 110:25 (2013)