NONEQUILIBRIUM STEADY-STATE IN A QUANTUM SYSTEM - ONE-DIMENSIONAL TRANSVERSE ISING-MODEL WITH ENERGY CURRENT

We study the nonequilibrium steady states of an Ising chain in a trans verse field h by investigating the effect of a field h, which drives t he current of energy. The zero-temperature, h-h phase diagram is deter mined exactly, and it is found that the energy current appears continu ously above a threshold lambda > lambda(c)(h). The long-range magnetic order (present for h < h(c),lambda < lambda(c)) is destroyed in the c urrent-carrying state where the correlations are characterized by powe r-law, oscillatory decay. The mechanism which generates the power-law correlations in the current-carrying state is discussed.