JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR: "Adiabatic dynamics in a spin-1 chain with uniaxial single-spin anisotropy"

[statphys]

JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR

Tuesday, 9 June 2009   -    12:00 hrs

(Attention! Unusual starting time!)

Seminar Room
ICTP Leonardo Building - 1st floor


Elena CANOVI
(S.I.S.S.A. - Trieste)

"Adiabatic dynamics in a spin-1 chain with
uniaxial single-spin anisotropy"

Abstract
  We numerically study the adiabatic quantum dynamics of an anisotropic 
spin-1 XY chain across a second order quantum phase transition. The 
system is driven out of equilibrium by performing a quench on the 
uniaxial single-spin anisotropy, that is supposed to vary linearly in 
time. We focus on the behavior of the excess energy, which quantifies 
the loss of adiabaticity of the system during the evolution. For small 
system sizes only the ground state and the first excited state 
effectively participate in the evolution, so the dynamics can be 
explained in terms of a Landau-Zener model, which describes an avoided 
level crossing between two levels. For sufficiently large system sizes, 
the excess energy after the quench admits a non trivial scaling behavior 
that is not predictable by standard Kibble-Zurek arguments for isolated 
critical points or extended critical regions. This emerges from a 
competing effect of many accessible low-lying excited states, inside the 
whole continuous line of critical points.