Gaplessness from disorder and quantum geometry in gapped superconductors
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arXiv
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910003889176576 |
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| author | Lesser, Omri Banerjee, Sagnik Wang, Xuepeng Kim, Jaewon Altman, Ehud Chowdhury, Debanjan |
| author_facet | Lesser, Omri Banerjee, Sagnik Wang, Xuepeng Kim, Jaewon Altman, Ehud Chowdhury, Debanjan |
| contents | It is well known that disorder can induce low-energy Andreev bound states in a sign-changing, but fully gapped, superconductor at $π-$junctions. Generically, these excitations are localized. Starting from a superconductor with a sign-changing and nodeless order parameter in the clean limit, here we demonstrate a mechanism for increasing the localization length associated with the low-energy Andreev bound states at a fixed disorder strength. We find that the Fubini-Study metric associated with the electronic Bloch wavefunctions controls the localization length and the hybridization between bound states localized at distinct $π-$junctions. We present results for the inverse participation ratio, superfluid stiffness, site-resolved and disorder-averaged spectral functions as a function of increasing Fubini-Study metric, which indicate an increased tendency towards delocalization. The low-energy properties resemble those of a dirty nodal superconductor with gapless Bogoliubov excitations. We place these results in the context of recent experiments in moire graphene superconductors. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_15891 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Gaplessness from disorder and quantum geometry in gapped superconductors Lesser, Omri Banerjee, Sagnik Wang, Xuepeng Kim, Jaewon Altman, Ehud Chowdhury, Debanjan Superconductivity Disordered Systems and Neural Networks Mesoscale and Nanoscale Physics Strongly Correlated Electrons It is well known that disorder can induce low-energy Andreev bound states in a sign-changing, but fully gapped, superconductor at $π-$junctions. Generically, these excitations are localized. Starting from a superconductor with a sign-changing and nodeless order parameter in the clean limit, here we demonstrate a mechanism for increasing the localization length associated with the low-energy Andreev bound states at a fixed disorder strength. We find that the Fubini-Study metric associated with the electronic Bloch wavefunctions controls the localization length and the hybridization between bound states localized at distinct $π-$junctions. We present results for the inverse participation ratio, superfluid stiffness, site-resolved and disorder-averaged spectral functions as a function of increasing Fubini-Study metric, which indicate an increased tendency towards delocalization. The low-energy properties resemble those of a dirty nodal superconductor with gapless Bogoliubov excitations. We place these results in the context of recent experiments in moire graphene superconductors. |
| title | Gaplessness from disorder and quantum geometry in gapped superconductors |
| topic | Superconductivity Disordered Systems and Neural Networks Mesoscale and Nanoscale Physics Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2505.15891 |