GEOMETRIC PHASE OF SPIN CHAIN SYSTEM IN THE NONEQUILIBRIUM THERMAL ENVIRONMENTS

In this paper, we investigate the nonequilibrium geometric phase (GP) of a spin chain system whose two end spins are respectively coupled to thermal reservoirs at different temperatures. In the spin chain, there exists the XX-type spin interaction and an external field is applied to each spin. An analytical expression for the GP is found in the weak coupling limit. The influences of various parameters on the deviation of GP from the unitary one are investigated. It is found that the GP is more stable against the decoherence when the external field is homogenously applied. In addition, the present result may provide a useful approach to the maintenance of GP in the nonequilibrium system.