13C NMR study of superconductivity near charge instability realized in beta"-(BEDT-TTF)4[(H3O)Ga(C2O4)3]C6H5NO2

Abstract

To investigate the superconducting (SC) state near a charge instability, we performed ^{13}C NMR experiments on the molecular superconductor beta"-(BEDT-TTF)_{4}[(H_{3}O)Ga(C_{2}O_{4})_{3}]C_{6}H_{5}NO_{2}, which exhibits a charge anomaly at 100 K. The Knight shift which we measured in the SC state down to 1.5 K demonstrates that Cooper pairs are in spin-singlet state. Measurements of the nuclear spin-lattice relaxation time reveal strong electron-electron correlations in the normal state. The resistivity increase observed below 10 K indicates that the enhanced fluctuation has an electric origin. We discuss the possibility of charge-fluctuation-induced superconductivity.

5 pages, 4 figures

References in corpus (6)

• Signatures of valence fluctuations in CeCu2Si2 under high pressure
• Superconductivity mediated by charge fluctuations in layered molecular crystals
• Fermi-surface topology and the effects of intrinsic disorder in a class of charge-transfer salts containing magnetic ions, β''-(BEDT-TTF)_4[(H_3O)M(C_2O_4)_3]Y
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Cited by in corpus (3)

• Anisotropic Fully-Gapped Superconductivity Possibly Mediated by Charge Fluctuations in a Nondimeric Organic Complex
• Effects of Electron Correlations and Chemical Pressures on Superconductivity of ${\beta }^{\prime \prime }$-type Organic Compounds
• Microscopic coexistence of superconductivity and charge order in organic superconductor ${\beta }^{\prime \prime }$-(BEDT-TTF)${}_4$[(H${}_3$O)Ga(C${}_2$O${}_4$)${}_3$]$\cdot$C${}_6$H${}_5$NO${}_2$