Europhys. Lett.
Volume 76, Number 2, October 2006
Page(s) 182 - 188
Section General
Published online 20 September 2006
Europhys. Lett., 76 (2), pp. 182-188 (2006)
DOI: 10.1209/epl/i2006-10270-x

Scaling of Berry's phase close to the Dicke quantum phase transition

F. Plastina1, G. Liberti1 and A. Carollo2

1  Dipartimento di Fisica, Università della Calabria and Istituto Nazionale di Fisica Nucleare, Gruppo collegato di Cosenza I-87036 Arcavacata di Rende, Cosenza, Italy
2  Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences - A-6020 Innsbruck, Austria

received 26 June 2006; accepted in final form 31 August 2006
published online 20 September 2006

We discuss the thermodynamic and finite-size scaling properties of the geometric phase in the adiabatic Dicke model, describing a quantum phase transition for an N qubit register coupled to a slow oscillator mode. We show that, in the thermodynamic limit, a non-zero Berry phase is obtained only if a path in parameter space is followed that encircles the critical point. Furthermore, we investigate the precursors of this critical behavior for a system with finite size and obtain the leading orders in the 1/N expansion of the Berry phase and its critical exponent.

03.65.Vf - Phases: geometric; dynamic or topological.
42.50.Fx - Cooperative phenomena in quantum optical systems.

© EDP Sciences 2006