Coexistence of full-gap superconductivity and pseudogap in two-dimensional fullerides

Abstract

Alkali-fulleride superconductors with a maximum critical temperature Tc of 40 K exhibit similar electronic phase diagram with unconventional high-Tc superconductors where the superconductivity resides proximate to a magnetic Mott-insulating state. However, distinct from cuprate compounds, which superconduct through two-dimensional (2D) CuO2 planes, alkali fullerides are attributed to the three-dimensional (3D) members of high-Tc family. Here, we employ scanning tunneling microscopy to show that trilayer K3C60 displays fully gapped strong coupling s-wave superconductivity that coexists spatially with a cuprate-like pseudogap state above Tc = 22 K and within vortices. A precise control of electronic correlations and doping reveals that superconductivity occurs near a superconductor-Mott insulator transition and reaches maximum at half-filling. The s-wave symmetry retains over the entire phase diagram, which, in conjunction with an abrupt decline of superconductivity below half-filling, demonstrates that alkali fullerides are predominantly phonon-mediated superconductors, although the multiorbital electronic correlations also come into play.

arXiv comment10 pages, 5 figures, supplementary materials

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• Experimental observation of Dirac cones in artificial graphene lattices
• Tuning the electronic states and superconductivity in alkali fulleride films
• Evidence for Band Renormalizations in Strong-coupling Superconducting Alkali-fulleride Films
• Entropy and electronic orders of the three-orbital Hubbard model with antiferromagnetic Hund coupling
• Eliashberg theory of the Jahn-Teller-Hubbard model
• Quantum spin driven Yu-Shiba-Rusinov multiplets and fermion-parity-preserving phase transition in K${}_3$C${}_{60}$
• Spin-orbital model for fullerides
• Universal approach to light driven "superconductivity" via preformed pairs
• Doping asymmetry and layer-selective metal-insulator transition in trilayer K${}_{3+x}$C${}_{60}$
• Infrared ellipsometry study of the charge dynamics in K3p-terphenyl
• Merohedral disorder and impurity impacts on superconductivity of fullerenes
• Superconducting fluctuations observed far above T${}_{\mathrm{c}}$ in the isotropic superconductor K${}_3$C${}_{60}$