Abstract
We investigate the superconductivity in the deuterated BEDT-TTF molecular substitution system κ-[(h8-BEDT-TTF)1−x(d8-BEDT-TTF)x]2Cu[N(CN)2]Br, where h8 and d8 denote fully hydrogenated and deuterated molecules, respectively. Systematic and wide-range (x=0–1) substitution can accurately control chemical pressure near the Mott boundary, which results in the modification of the superconductivity. After cooling slowly, an increase in Tc observed up to x∼0.1 is evidently caused by the chemical pressure effect. Neither a reduction of Tc nor a suppression of superconducting volume fraction is found below x∼0.5. This demonstrates that the effect of disorder by substitution is negligible in the present system. With further increase in x, both Tc and superconducting volume fraction start to decrease toward values at x=1.
