Multiple Superconducting Phases in Palladium Deuteride Induced by Nuclear-Spin Isotope Effect

Abstract

We study the superconducting properties of high-quality PdD${}_x$ films. The resistivity shows a sharp drop at $T$ $\sim$1.7 K, marking the superconducting transition. However, a finite resistivity persists and vanishes at $\sim$0.6 K. The temperature and magnetic-field dependences of the resistivity exhibit multiple anomalies within the superconducting state, revealing distinct superconducting phases. Such anomalies are absent in PdH${}_x$ films. These results demonstrate a clear qualitative difference between the superconducting phase diagrams of PdD${}_x$ and PdH${}_x$, highlighting the role of nuclear-spin isotope effects.

6 pages