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arXiv · 1911.04599

Effects of Electron Correlations and Chemical Pressures on Superconductivity of $\beta^{\prime\prime}$-type Organic Compounds

S. Imajo·H. Akutsu·A. Akutsu-Sato·A. L. Morritt·L. Martin·Y. Nakazawa
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Abstract

We investigate low-temperature electronic states of the series of organic conductors $\beta^{\prime\prime}$-(BEDT-TTF)$_4$[(H$_3$O)M(C$_2$O$_4$)$_3$]G, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, and 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 positive correlation with the superconducting transition temperature $T_{\rm c}$. Analyses of temperature and magnetic field dependences of the electrical resistance including the Shubnikov-de Haas oscillations elucidates that the variation of charge disproportionation, 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.

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S. Imajo, H. Akutsu, A. Akutsu-Sato, A. L. Morritt, L. Martin, Y. Nakazawa. 2019-11-11. Effects of Electron Correlations and Chemical Pressures on Superconductivity of $\beta^{\prime\prime}$-type Organic Compounds. https://doi.org/10.1103/physrevresearch.1.033184

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