Inverse isotope effect in organic superconductors : new findings and implications

摘要

The inverse deuterium isotope effect, previously found in K-(BEDT-TTF)(sub 2)CU(NCS)(sub 2), is also found in two other BEDT-TTF-based superconductors with different packing motifs and different types of anions. Remarkably, the magnitude of the isotope shift is essentially identical in all three superconductors, ca. +0.26 (+-) 0.06 K. These results, when taken together with the recent results of Lang et al. on the uniaxial pressure derivatives of T(sub c), suggest that the inverse isotope effect may not have a direct relationship to the pairing mechanism but instead is a reflection of the change in the internal lattice pressure.