Phase transition in quasi-flat band superconductors
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866912498717818880 |
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| author | Zyuzin, A. A. Zyuzin, A. Yu. |
| author_facet | Zyuzin, A. A. Zyuzin, A. Yu. |
| contents | We investigate superconductivity in a two-dimensional material described by a two-band heavy-fermion model, where hybridization between a dispersive band and a flat band introduces a quasi-flat dispersion to the otherwise localized flat-band electrons. The enhanced density of states in the quasi-flat band raises the crossover temperature for an inhomogeneous preformed Cooper pair state. The superconducting phase stiffness and the Berezinskii-Kosterlitz-Thouless (BKT) temperature are governed by the Fermi surface contribution induced by hybridization. We compute the crossover and BKT temperatures, revealing a dome-like dependence on doping. When the pairing amplitude exceeds the energy width of the quasi-flat band, superconductivity is suppressed, and the inhomogeneous pairing regime expands linearly with increasing interaction strength. However, in the opposite case, the BKT temperature reaches a maximum value that is only numerically less than the energy width of the quasi-flat band. We also discuss our results in the context of superconductivity in graphene-based systems. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2501_17314 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Phase transition in quasi-flat band superconductors Zyuzin, A. A. Zyuzin, A. Yu. Superconductivity Mesoscale and Nanoscale Physics We investigate superconductivity in a two-dimensional material described by a two-band heavy-fermion model, where hybridization between a dispersive band and a flat band introduces a quasi-flat dispersion to the otherwise localized flat-band electrons. The enhanced density of states in the quasi-flat band raises the crossover temperature for an inhomogeneous preformed Cooper pair state. The superconducting phase stiffness and the Berezinskii-Kosterlitz-Thouless (BKT) temperature are governed by the Fermi surface contribution induced by hybridization. We compute the crossover and BKT temperatures, revealing a dome-like dependence on doping. When the pairing amplitude exceeds the energy width of the quasi-flat band, superconductivity is suppressed, and the inhomogeneous pairing regime expands linearly with increasing interaction strength. However, in the opposite case, the BKT temperature reaches a maximum value that is only numerically less than the energy width of the quasi-flat band. We also discuss our results in the context of superconductivity in graphene-based systems. |
| title | Phase transition in quasi-flat band superconductors |
| topic | Superconductivity Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2501.17314 |