Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene
Recent scanning tunneling microscopy experiments in twisted bilayer [K. P. Nuckolls et al., Nature (London) 620, 525 (2023)] and trilayer [H. Kim et al., Nature (London) 623, 942 (2023)] graphene have revealed the ubiquity of Kekulé charge-density wave order in magic-angle graphene. Most samples are...
| Main Authors: | , , , , , |
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| Format: | Journal article |
| Language: | English |
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American Physical Society
2024
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| _version_ | 1826314448370925568 |
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| author | Kwan, YH Wagner, G Bultinck, N Simon, SH Berg, E Parameswaran, SA |
| author_facet | Kwan, YH Wagner, G Bultinck, N Simon, SH Berg, E Parameswaran, SA |
| author_sort | Kwan, YH |
| collection | OXFORD |
| description | Recent scanning tunneling microscopy experiments in twisted bilayer [K. P. Nuckolls et al., Nature (London) 620, 525 (2023)] and trilayer [H. Kim et al., Nature (London) 623, 942 (2023)] graphene have revealed the ubiquity of Kekulé charge-density wave order in magic-angle graphene. Most samples are moderately strained and show “incommensurate Kekulé spiral” (IKS) order involving a graphene-scale charge density distortion uniaxially modulated on the scale of the moiré superlattice, in accord with theoretical predictions. However, ultralow strain bilayer samples instead show graphene-scale Kekulé charge order that is uniform on the moiré scale. This order, especially prominent near filling factor 𝜈=−2, is unanticipated by theory which predicts a time-reversal breaking Kekulé current order at low strain. We show that including the coupling of moiré electrons to graphene-scale optical zone-corner (ZC) phonons stabilizes a uniform Kekulé charge ordered state at |𝜈|=2 with a quantized topological (spin or anomalous Hall) response. Our work clarifies how this phonon-driven selection of electronic order emerges in the strong-coupling regime of moiré graphene. |
| first_indexed | 2024-09-25T04:34:11Z |
| format | Journal article |
| id | oxford-uuid:df01c58e-c581-4a3f-9492-f98deee23ce7 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:34:11Z |
| publishDate | 2024 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | oxford-uuid:df01c58e-c581-4a3f-9492-f98deee23ce72024-09-05T12:17:22ZElectron-phonon coupling and competing Kekulé orders in twisted bilayer grapheneJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:df01c58e-c581-4a3f-9492-f98deee23ce7EnglishSymplectic ElementsAmerican Physical Society2024Kwan, YHWagner, GBultinck, NSimon, SHBerg, EParameswaran, SARecent scanning tunneling microscopy experiments in twisted bilayer [K. P. Nuckolls et al., Nature (London) 620, 525 (2023)] and trilayer [H. Kim et al., Nature (London) 623, 942 (2023)] graphene have revealed the ubiquity of Kekulé charge-density wave order in magic-angle graphene. Most samples are moderately strained and show “incommensurate Kekulé spiral” (IKS) order involving a graphene-scale charge density distortion uniaxially modulated on the scale of the moiré superlattice, in accord with theoretical predictions. However, ultralow strain bilayer samples instead show graphene-scale Kekulé charge order that is uniform on the moiré scale. This order, especially prominent near filling factor 𝜈=−2, is unanticipated by theory which predicts a time-reversal breaking Kekulé current order at low strain. We show that including the coupling of moiré electrons to graphene-scale optical zone-corner (ZC) phonons stabilizes a uniform Kekulé charge ordered state at |𝜈|=2 with a quantized topological (spin or anomalous Hall) response. Our work clarifies how this phonon-driven selection of electronic order emerges in the strong-coupling regime of moiré graphene. |
| spellingShingle | Kwan, YH Wagner, G Bultinck, N Simon, SH Berg, E Parameswaran, SA Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene |
| title | Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene |
| title_full | Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene |
| title_fullStr | Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene |
| title_full_unstemmed | Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene |
| title_short | Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene |
| title_sort | electron phonon coupling and competing kekule orders in twisted bilayer graphene |
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