Pressure-induced superconductivity in the spin-ladder cuprate

Pressure-induced superconductivity in a spin-ladder cuprate Sr2Ca12Cu24O41 was investigated on a microscopic level by using 63Cu nuclear magnetic resonance (NMR) under a pressure of 3.5 GPa. We found a fully gapped superconducting state, and the superconductivity is stable at magnetic fields close to the conventional Pauli limit. The superconducting gap was observed in addition to a spin gap which occurs in a separated temperature range.