Interlayer coupling effect in high-Tc superconductors probed by YBa2Cu3O7-x/PrBa2Cu3O7-x superlattices

The effect of coupling between layers of the high-Tc superconductors was studied by varying both the YBa2Cu3O7-x and PrBa2Cu3O7-x layer thicknesses in YBa2Cu3O7-x/PrBa2Cu3O7-x superlattices. Superconductivity was found even when the YBa2Cu3O7-x layers had nominal thicknesses as small as 12 (one unit-cell thickness) but coupling between unit-cell layers is needed to achieve a Tc of 90 K. The decrease of Tc in isolated YBa2Cu3O7-x layers with increasing sheet resistance is on the same scale of about Latin small letter h with stroke/e2 as observed for ordinary superconductors. © 1990 The American Physical Society.