Comparative pressure studies of the superconducting transition temperature in isotopically substituted samples of κ-(BEDT-TTF)2Cu(SCN)2

We determined the pressure dependence of the superconducting transition temperatures T-c, of the organic superconductor kappa-(BEDT-TTF)(2)Cu(SCN)(2) for three different isotopic compositions using helium as a pressure medium. These measurements demonstrated that, given identical measurement conditions, the pressure dependence of T-c is independent of the isotopic composition of the material. Assuming that these isotopically different materials have an identical unit cell compressibility, it is found that for all three materials T-c scales linearly with the quasi-two-dimensional unit cell area, and is thus inversely proportional to the quasi-two-dimensional carrier density in kappa-(BED-TTTF)(2)Cu(SCN)(2). (C) 2003 Elsevier B.V. All rights reserved.