Enhanced transition temperature in a quantum confined high-<i>T</i>_c superconductor

A slight enhancement of the onset transition temperature Tc has been observed in quantum dots of the high-Tc superconductor yttrium–barium–copper oxide (Y1Ba2Cu3O7−δ). The dots were formed when YBCO particles (diameter ≤600 nm) were exposed to an RF plasma to produce a Coulomb crystal. The plasma damages the particles and causes 20–25 nm sized isolated islands of the correct 1-2-3 stoichiometry to segregate within each particle. We believe that quantum confinement of carriers within these islands leads to discretization of the quasi-particle density-of-states which can account for the slight increase in the transition temperature.