Effects of electron correlations and chemical pressures on superconductivity of β′′-type organic compounds

Shusaku Imajo; Hiroki Akutsu; Akane Akutsu-Sato; Alexander L. Morritt; Lee Martin; Yasuhiro Nakazawa

doi:10.1103/PhysRevResearch.1.033184

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Effects of electron correlations and chemical pressures on superconductivity of β′′-type organic compounds

Shusaku Imajo, Hiroki Akutsu, Akane Akutsu-Sato, Alexander L. Morritt, Lee Martin, Yasuhiro Nakazawa

DOI 10.1103/PhysRevResearch.1.033184 · Physical Review Research

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Abstract

We investigate low-temperature electronic states of the series of organic conductors β′′−[bis(ethylenedithio)tetrathiafulvalene]4[(H3O)M(C2O4)3]G, where M and G represent trivalent metal ions and guest organic molecules, respectively. Our structural analyses reveal that the replacement of M and G give rise to systematic change in the cell parameters, especially in the b-axis length, which has a positive correlation with the superconducting transition temperature Tc. Analysis of temperature and magnetic field dependences of the electrical resistance including the Shubnikov–de Haas oscillations elucidates that the variation of charge disproportionation, the effective mass, and the number of itinerant carriers can be systematically explained by the change of the b-axis length. The changes of the transfer integrals induced by stretching/compressing the b axis are confirmed by the band calculation. We discuss that electron correlations in quarter-filled electronic bands lead to charge disproportionation and the possibility of a novel pairing mechanism of superconductivity mediated by charge degrees of freedom.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
β''-(BEDT-TTF)4[(H3O)Fe(C2O4)3]C6H5CN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.2	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ga(C2O4)3]C6H5NO2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ga(C2O4)3]DMF Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.5	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ga(C2O4)3]C6H5Br Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Rh(C2O4)3]C6H5Br Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.9	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ru(C2O4)3]C6H5Br Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.8	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ga(C2O4)3]C5H5N Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.5	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ga(C2O4)3]C6H5I Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.4	Pressure not reported	onset
β''-(BEDT-TTF)4[(H3O)Ga(C2O4)3]2-C5H4ClN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.7	Pressure not reported	onset