Spin-fluctuation-mediated chiral $d+id'$-wave superconductivity in the $α$-$\mathcal{T}_3$ lattice with an incipient flat band
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| Format: | Preprint |
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2025
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| _version_ | 1866911561710305280 |
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| author | Kakoi, Masataka Kuroki, Kazuhiko |
| author_facet | Kakoi, Masataka Kuroki, Kazuhiko |
| contents | We study anisotropic superconductivity in the nearly quarter-filled $α$-$\mathcal{T}_3$ 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 $\mathbf{q}=\mathbf{0}$ 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_14379 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Spin-fluctuation-mediated chiral $d+id'$-wave superconductivity in the $α$-$\mathcal{T}_3$ lattice with an incipient flat band Kakoi, Masataka Kuroki, Kazuhiko Superconductivity Strongly Correlated Electrons We study anisotropic superconductivity in the nearly quarter-filled $α$-$\mathcal{T}_3$ 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 $\mathbf{q}=\mathbf{0}$ 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. |
| title | Spin-fluctuation-mediated chiral $d+id'$-wave superconductivity in the $α$-$\mathcal{T}_3$ lattice with an incipient flat band |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2512.14379 |