Quantum Institute: Visitor Schedule

The Quantum Lunch is regularly held on Thursdays in the Theoretical Division Conference Room, TA-3, Building 123, Room 121.
For more information, contact Diego Dalvit.

August 21, 2007
Tuesday, 1:00PM
T-CLNS Conference Room, TA-3-1690

Anatoli Sergeevich Polkovnikov,
Boston University

Breakdown of the Adiabatic Limit in Low Dimensional Gapless Systems

Abstract

It is generally believed that a generic system can be reversibly transformed from one state into another by sufficiently slow change of parameters and that the entropy of the system is conserved in such a slow (adiabatic) process. A general argument favoring this assertion is based on the possibility of expansion of the entropy generation into the Taylor series in the ramp speed. Here we show that this general argument is indeed valid at high enough dimensions. However, in low dimensional systems this argument can break down. We identify three possible generic regimes of a system response to a slow ramp: (A) mean-field regime, where the generated entropy density is an analytic function of the ramp speed, ({B) non-analytic regime, where the generated entropy vanishes with some universal power less than two of the ram speed, and (C) non-adiabatic regime where the excess entropy vanishes as a product of powers of the ramp speed and the system size. In the third regime no matter how slow the system is driven the entropy will not be conserved in the thermodynamic limit. We give specific examples where we all three regimes are realized and support our results by numerical simulations.