Incommensurate inter-valley coherent states in ABC graphene: collective modes and superconductivity
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866909725592911872 |
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| author | Vituri, Yaar Xiao, Jiewen Pareek, Keshav Holder, Tobias Berg, Erez |
| author_facet | Vituri, Yaar Xiao, Jiewen Pareek, Keshav Holder, Tobias Berg, Erez |
| contents | Recent experiments in ABC trilayer graphene detected superconductivity on the border of a phase transition to a symmetry-broken phase. In this work, we use unrestricted Hartree-Fock to study the nature of this phase. We find a close competition between two incommensurate inter-valley coherent (IVC) phases: an IVC crystal where the ordering occurs at multiple wavevectors, and an IVC spiral with a single ordering wavevector. Focusing on one of the regimes where superconductivity is observed experimentally, we find a continuous (or very weakly first order) transition between a half metallic phase to an IVC crystal, followed by a first-order transition into an IVC spiral. Using time-dependent Hartree-Fock, we study the collective mode spectrum in the half-metalic phase. We find a soft inter-valley mode that can mediate superconductivity in a narrow sliver of density near the continuous transition, with a Tc that can reach a few hundreds of mK and a sign-changing s-wave order parameter. The spin stiffness in the half metal phase is found to be surprisingly low, of the order of a few degrees Kelvin. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2408_10309 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Incommensurate inter-valley coherent states in ABC graphene: collective modes and superconductivity Vituri, Yaar Xiao, Jiewen Pareek, Keshav Holder, Tobias Berg, Erez Strongly Correlated Electrons Mesoscale and Nanoscale Physics Superconductivity Recent experiments in ABC trilayer graphene detected superconductivity on the border of a phase transition to a symmetry-broken phase. In this work, we use unrestricted Hartree-Fock to study the nature of this phase. We find a close competition between two incommensurate inter-valley coherent (IVC) phases: an IVC crystal where the ordering occurs at multiple wavevectors, and an IVC spiral with a single ordering wavevector. Focusing on one of the regimes where superconductivity is observed experimentally, we find a continuous (or very weakly first order) transition between a half metallic phase to an IVC crystal, followed by a first-order transition into an IVC spiral. Using time-dependent Hartree-Fock, we study the collective mode spectrum in the half-metalic phase. We find a soft inter-valley mode that can mediate superconductivity in a narrow sliver of density near the continuous transition, with a Tc that can reach a few hundreds of mK and a sign-changing s-wave order parameter. The spin stiffness in the half metal phase is found to be surprisingly low, of the order of a few degrees Kelvin. |
| title | Incommensurate inter-valley coherent states in ABC graphene: collective modes and superconductivity |
| topic | Strongly Correlated Electrons Mesoscale and Nanoscale Physics Superconductivity |
| url | https://arxiv.org/abs/2408.10309 |