Dynamical non-ergodic scaling in continuous finite-order quantum phase transitionsS. Deng1, G. Ortiz2 and L. Viola1
1 Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory - Hanover, NH 03755, USA
2 Department of Physics, Indiana University - Bloomington, IN 47405, USA
received 23 July 2008; accepted in final form 13 November 2008; published December 2008
published online 12 January 2009
We investigate the emergence of universal dynamical scaling in quantum critical spin systems adiabatically driven out of equilibrium, with emphasis on quench dynamics which involves non-isolated critical points (i.e., critical regions) and cannot be a priori described through standard scaling arguments nor time-dependent perturbative approaches. Comparing to the case of an isolated quantum critical point, we find that non-equilibrium scaling behavior of a large class of physical observables may still be explained in terms of equilibrium critical exponents. However, the latter are in general non-trivially path-dependent, and detailed knowledge about the time-dependent excitation process becomes essential. In particular, we show how multiple level crossings within a gapless phase may completely suppress excitation depending on the control path. Our results typify non-ergodic scaling in continuous finite-order quantum phase transitions.
73.43.Nq - Quantum phase transitions.
05.70.Jk - Critical point phenomena.
75.10.Jm - Quantized spin models.
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