Substitution Effect by Deuterated Donors on Superconductivity in $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br

Abstract

We investigate the superconductivity in the deuterated BEDT-TTF molecular substitution system $\kappa$-[(h8-BEDT-TTF)${}_{1-x}$(d8-BEDT-TTF)${}_x$]${}_2$Cu[N(CN)${}_2$]Br, where h8 and d8 denote fully hydrogenated and deuterated molecules, respectively. Systematic and wide range ($x$ = 0 -- 1) substitution can control chemical pressure finely near the Mott boundary, which results in the modification of the superconductivity. After cooling slowly, the increase of $T_{\text{c}}$ observed up to $x\sim$ 0.1 is evidently caused by the chemical pressure effect. Neither reduction of $T_{\text{c}}$ nor suppression of superconducting volume fraction is found below $x\sim$ 0.5. This demonstrates that the effect of disorder by substitution is negligible in the present system. With further increase of $x$, both $T_{\text{c}}$ and superconducting volume fraction start to decrease toward the values in $x$ = 1.

J. Phys. Soc. Jpn

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• Mott transition and transport crossovers in the organic compound $\kappa -(BEDT-TTF{)}_{2}Cu[N(CN{)}_2]Cl$
• Mott Transition, Compressibility Divergence and P-T Phase Diagram of Layered Organic Superconductors: An Ultrasonic Investigation
• The Dependence of the Superconducting Transition Temperature of Organic Molecular Crystals on Intrinsically Non-Magnetic Disorder: a Signature of either Unconventional Superconductivity or Novel Local Magnetic Moment Formation

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