Quantum Ratchets

We investigate quantum Brownian motion in adiabatically rocked ratchet systems. Above a cross temperatureTc tunneling events are rare, yet they already substantially enhance the classical par current. BelowTc, quantum tunneling prevails and the classical predictions grossly underestimate transport. Upon approaching T ­ 0 the quantum current exhibits a tunneling induced reversal, an tends to a finite limit. [S0031-9007(97)03540-0]