Extraordinary $\pi$-Electron Superconductivity Emerging from a Quantum Spin Liquid

Abstract

Quantum spin liquids (QSLs), in which spins are highly entangled, have been considered a groundwork for generating exotic superconductivity.Despite numerous efforts, superconductivity emerging from QSLs has been unrealized in actual materials due to the difficulties in stabilizing QSL states with metallic conductivity.Recently, an organic compound, $\kappa$-(BEDT-TTF)${}_4$Hg${}_{2.89}$Br${}_8$, with a nearly regular triangular lattice of molecular dimers was recognized as a candidate for doped QSLs. In this study, we report an unusual superconducting phase of $\kappa$-(BEDT-TTF)${}_4$Hg${}_{2.89}$Br${}_8$: unexpectedly large ratios of the upper critical field to the critical temperature $H_{c2}$/$T_{\mathrm{c}}$ in fields not only parallel but also perpendicular to the two-dimensional conducting layers and a very wide region of fluctuating superconductivity above $T_{\mathrm{c}}$.Our results reveal that these peculiarities arise from strong electron correlations and possible quantum criticality unique to the doped QSL state, leading to a heavy mass of itinerant carriers and a large superconducting energy gap.

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Cited by in corpus (6)

• When Superconductivity Crosses Over: From BCS to BEC
• Mott-driven BEC-BCS crossover in a doped spin liquid candidate, kappa-(BEDT-TTF)4Hg2.89Br8
• Superconductivity in doped triangular Mott insulators: the roles of parent spin backgrounds and charge kinetic energy
• Pseudogap formation in organic superconductors
• Test for BCS-BEC Crossover in the Cuprate Superconductors
• Systematic evolution of superconducting pairing strength and Seebeck coefficients in correlated infinite-layer La${}_{1-x}$Sr${}_x$NiO${}_2$