Enhanced transition temperature in a quantum confined high-T-c superconductor

A slight enhancement of the onset transition temperature T-c has been obser ved in quantum dots of the high-T-c superconductor yttrium-barium-copper ox ide (Y1Ba2Cu3O7-delta). The dots were formed when YBCO particles (diameter less than or equal to 600 nm) were exposed to an RF plasma to produce a Cou lomb crystal. The plasma damages the particles and causes 20-25 nm sized is olated islands of the correct 1-2-3 stoichiometry to segregate within each particle. We believe that quantum confinement of carriers within these isla nds leads to discretization of the quasi-particle density-of-states which c an account for the slight increase in the transition temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.