Vacuum induced Spin-1/2 Berry phase
  We calculate the Berry phase of a spin-1/2 particle in a magnetic field considering the quantum nature of the field. The phase reduces to the standard Berry phase in the semiclassical limit and eigenstate of the particle acquires a phase in the vacuum. We also show how to generate a vacuum induced Berry phase considering two quantized modes of the field which has a interesting physical interpretation. 
I. Fuentes-Guridi, A. Carollo, S. Bose and V. Vedral