ar X iv : c on d - m at / 9 50 50 97 v 1 2 2 M ay 1 99 5 Peltier effect in NS microcontacts

We have calculated the heat current in the normal metal/insulator/ supercon-ductor contacts with arbitrary transparency of the insulator barrier. In the tunneling limit (small transparencies), the heat flow out of the normal metal reaches its maximum at temperature T ≃ 0.3∆. At higher values of transparency , the interplay between single-particle tunneling and Andreev reflection determines optimum transparency which maximizes the density of heat flow out of the normal metal. In clean contacts, the optimum transparency is about 0.1 at T = 0.3∆ and decreases with temperature roughly as (T /∆) 3/2. In disordered contacts, disorder enhances Andreev reflection and shifts the optimum point towards smaller transparencies. The optimal ratio of the barrier resistance to the resistance of the normal electrode is R N /R T ≃ 0.01 at T = 0.3∆ and decreases with temperature similarly to clean contacts. For disordered contacts we also plot current-voltage characteristics for arbitrary values of the ratio R N /R T .