A spin ladder compound doubles its superconducting TC under a gentle uniaxial pressure
Discovery of new high TC superconductors, with TC > 23 K, continues to be challenging. We have doubled the existing TC of single crystal Sr3Ca11Cu24O41, a spin ladder cuprate, from 12K to 24K, using a gentle uniaxial pressure ~ 0.06 GPa. In contrast, earlier works used a nearly 100 times larger hydrostatic pressure 5 GPa, only to reach a maximum TC ~ 12K. Our work exposes large and nearly equal, but opposing contributions to changes in TC, arising from compressions along and perpendicular to ladder planes, in hydrostatic pressure experiments. In our resistivity measurements, uniaxial pressure applied along ladder planes increase TC, while that perpendicular to ladder planes decrease TC. Our findings i) offers a new hope for further increase in TC in spin ladder compounds and ii) calls for a large shift in phase boundaries of the currently accepted pressure-temperature phase diagram.