THERMOELECTRIC-POWER - A SIMPLE, INSTRUCTIVE PROBE OF HIGH-T-C SUPERCONDUCTORS

The thermoelectric power S(T) is studied for YBa2Cu3O7-delta and YBa2Cu4O8 as a function of Zn substitution acid hole concentration p. A strong enhancement in S(T) is correlated with the smooth opening of an energy gap in the normal-state spectrum, as observed from NMR and heat capacity data, which appears to be responsible for the p-dependent variation in T-c. The data are consistent with the local suppression of this energy gap in the immediate neighborhood of a Zn atom. Studies of S(T) provide a simple means to explore the energy scales associated with the superconducting phase diagram and give some key insights into the origins of cuprate superconductivity.