Pyroelectric effect measurements in YBa₂Cu₃O_6+y and La₂CuO₄ materials

Abstract

We report measurements of the pyroelectric effect on a number of high-quality YBa₂Cu₃O_6+y and La₂CuO₄ single crystals. Upon cooling, the pyroelectric signal is found to persist from room temperature to the superconducting transition temperature, and vanishes below T_c in superconducting samples of YBa₂Cu₃O_6+y. In some samples, we found the sign of the polarization to change with temperature. Polarization reversal accompanied with a large increase in pyroelectric response was observed under external electric field. We also found the pyroelectric coefficient in YBa₂Cu₃O_6+y to be proportional with the oxygen defect concentration y.