Spin-fluctuation-mediated chiral d+id′-wave superconductivity in the α–T3 lattice with an incipient flat band

Masataka Kakoi; Kazuhiko Kuroki

doi:10.1103/2lth-6k7b

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Spin-fluctuation-mediated chiral d+id′-wave superconductivity in the α–T3 lattice with an incipient flat band

Masataka Kakoi, Kazuhiko Kuroki

DOI 10.1103/2lth-6k7b · Physical Review B

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Abstract

We study anisotropic superconductivity in the nearly quarter-filled α–T3 lattice. We analyze an extended Hubbard model with off-site attractive interactions within the mean-field framework and find two distinct chiral d+id′-wave superconducting phases characterized by different Chern numbers. We further investigate the superconducting mechanism mediated by spin fluctuations arising from purely repulsive interactions by applying the fluctuation-exchange (FLEX) approximation to the Hubbard model. The gap symmetry obtained by solving the linearized Eliashberg equation is d-wave, which corresponds to a d+id′-wave superconducting state with a Chern number of 8, including the spin degree of freedom. The q=0 antiferromagnetic spin fluctuation, which possesses the largest spectral weight at finite energies arising from the incipient flat band, gives rise to an effective spin-singlet pairing glue between rim sites.

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