THERMOELECTRIC AND THERMOPHASE EFFECTS IN JOSEPHSON-JUNCTIONS

We study the thermoelectric properties of a superconductor-insulator-s uperconductor Josephson junction. The total electrical current across the junction is composed of three parts: a normal current, a Josephson current, and an interference current. We show that only the normal pa rt contributes to a thermocurrent (i.e., an electrical current that fl ows in response to a temperature drop). The fact that the interference current has no thermoelectric properties provides insight into the ph ysical nature of this term. We distinguish between two mechanisms for the thermocurrent: one is the normal thermoelectric tunneling current; the other is a transport phenomenon, which ensues from a nonequilibri um (charge-imbalance) state in the bulk superconductors comprising the junction. The latter effect gives rise to a phase-dependent thermocur rent. Finally, we consider an open-circuit Josephson junction biased b y a temperature drop. The possible steady states of the system are stu died using the resistively shunted junction model. In particular, we c onsider the zero-voltage state which corresponds to canceling of the q uasiparticle and condensate currents. We call this a thermophase effec t. Experimental setups are suggested in order to detect this effect.