The dynamics of an asymmetric double-well system coupled to a heat bath is studied at low temperatures where transitions between the wells involve quantum tunneling. The time evolution of the occupation probabilities of the wells is calculated by means of instanton techniques. For a wide range of parameters incoherent relaxation is found at a rate whose dependence both on temperature and bias is nonanalytic, in general.

• Received 26 December 1984

DOI:https://doi.org/10.1103/PhysRevLett.54.1605