Terahertz photocurrent probe of quantum geometry and interactions in magic-angle twisted bilayer graphene
Source abstract
Abstract
Moiré materials represent strongly interacting electron systems bridging topological and correlated physics. Despite notable advances, decoding wavefunction properties underlying the quantum geometry remains challenging. Here we utilize polarization-resolved photocurrent measurements to probe magic-angle twisted bilayer graphene, leveraging its sensitivity to the Berry connection that encompasses quantum 'textures' of electron wavefunctions. Using terahertz light resonant with optical transitions of its flat bands, we observe bulk photocurrents driven by broken symmetries and reveal the interplay between electron interactions and quantum geometry. We observe inversion-breaking gapped states undetectable through quantum transport, sharp changes in the polarization axes caused by interaction-induced band renormalization and recurring photocurrent patterns at integer filling factors of the moiré unit cell that track the evolution of quantum geometry through the cascade of phase transitions. The large and tunable terahertz response intrinsic to flat-band systems offers direct insights into the quantum geometry of interacting electrons and paves the way for innovative terahertz quantum technologies.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Graphene research and applications · Topological Materials and Phenomena · Plasmonic and Surface Plasmon Research
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (56)
Show source-provided references
1. Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).10.1038/nature26160 ↗
2. Cao, Y. et al. Correlated insulator behaviour at half-filling in magic-angle graphene superlattices. Nature 556, 80–84 (2018).10.1038/nature26154 ↗
3. Andrei, E. Y. & MacDonald, A. H. Graphene bilayers with a twist. Nat. Mater. 19, 1265–1275 (2020).10.1038/s41563-020-00840-0 ↗
4. Sharpe, A. L. et al. Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene. Science 365, 605–608 (2019).10.1126/science.aaw3780 ↗
5. Serlin, M. et al. Intrinsic quantized anomalous Hall effect in a moiré heterostructure. Science 367, 900–903 (2020).10.1126/science.aay5533 ↗
6. Stepanov, P. et al. Competing zero-field chern insulators in superconducting twisted bilayer graphene. Phys. Rev. Lett. 127, 197701 (2021).10.1103/PhysRevLett.127.197701 ↗
7. Andrei, E. Y. et al. The marvels of moiré materials. Nat. Rev. Mater. 6, 201–206 (2021).10.1038/s41578-021-00284-1 ↗
8. Tschirhart, C. L. et al. Imaging orbital ferromagnetism in a moiré Chern insulator. Science 372, 1323–1327 (2021).10.1126/science.abd3190 ↗
9. Grover, S. et al. Chern mosaic and Berry-curvature magnetism in magic-angle graphene. Nat. Phys. 18, 885–892 (2022).10.1038/s41567-022-01635-7 ↗
10. Cea, T., Pantaleón, P. A. & Guinea, F. Band structure of twisted bilayer graphene on hexagonal boron nitride. Phys. Rev. B 102, 155136 (2020).10.1103/PhysRevB.102.155136 ↗
11. Kazmierczak, N. P. et al. Strain fields in twisted bilayer graphene. Nat. Mater. 20, 956–963 (2021).10.1038/s41563-021-00973-w ↗
12. Carr, S., Fang, S., Zhu, Z. & Kaxiras, E. Exact continuum model for low-energy electronic states of twisted bilayer graphene. Phys. Rev. Res. 1, 13001 (2019).10.1103/PhysRevResearch.1.013001 ↗
13. Ma, Q., Krishna Kumar, R., Xu, S.-Y., Koppens, F. H. L. & Song, J. C. W. Photocurrent as a multiphysics diagnostic of quantum materials. Nat. Rev. Phys. 5, 170–184 (2023).10.1038/s42254-022-00551-2 ↗
14. Ma, Q., Grushin, A. G. & Burch, K. S. Topology and geometry under the nonlinear electromagnetic spotlight. Nat. Mater. 20, 1601–1614 (2021).10.1038/s41563-021-00992-7 ↗
15. Dai, Z. & Rappe, A. M. Recent progress in the theory of bulk photovoltaic effect. Chem. Phys. Rev. 4, 11303 (2023).10.1063/5.0101513 ↗
16. Nakamura, M. et al. Shift current photovoltaic effect in a ferroelectric charge-transfer complex. Nat. Commun. 8, 281 (2017).
17. Ma, C. et al. Intelligent infrared sensing enabled by tunable moiré quantum geometry. Nature 604, 266–272 (2022).10.1038/s41586-022-04548-w ↗
18. Duan, J. et al. Giant second-order nonlinear Hall effect in twisted bilayer graphene. Phys. Rev. Lett. 129, 186801 (2022).10.1103/PhysRevLett.129.186801 ↗
19. Chaudhary, S., Lewandowski, C. & Refael, G. Shift-current response as a probe of quantum geometry and electron-electron interactions in twisted bilayer graphene. Phys. Rev. Res. 4, 013164 (2022).10.1103/PhysRevResearch.4.013164 ↗
20. Kaplan, D., Holder, T. & Yan, B. Twisted photovoltaics at terahertz frequencies from momentum shift current. Phys. Rev. Res. 4, 013209 (2022).10.1103/PhysRevResearch.4.013209 ↗
21. Arora, A., Kong, J. F. & Song, J. C. W. Strain-induced large injection current in twisted bilayer graphene. Phys. Rev. B 104, L241404 (2021).10.1103/PhysRevB.104.L241404 ↗
22. Pantaleón, P. A., Low, T. & Guinea, F. Tunable large Berry dipole in strained twisted bilayer graphene. Phys. Rev. B 103, 205403 (2021).10.1103/PhysRevB.103.205403 ↗
23. Lu, X. et al. Superconductors, orbital magnets and correlated states in magic-angle bilayer graphene. Nature 574, 653–657 (2019).10.1038/s41586-019-1695-0 ↗
24. Xie, Y. et al. Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene. Nature 572, 101–105 (2019).10.1038/s41586-019-1422-x ↗
25. Wong, D. et al. Cascade of electronic transitions in magic-angle twisted bilayer graphene. Nature 582, 198–202 (2020).10.1038/s41586-020-2339-0 ↗
26. Zondiner, U. et al. Cascade of phase transitions and Dirac revivals in magic-angle graphene. Nature 582, 203–208 (2020).10.1038/s41586-020-2373-y ↗
27. Li, G. et al. Infrared spectroscopy for diagnosing superlattice minibands in twisted bilayer graphene near the magic angle. Nano Lett. 24, 15956–15963 (2024).10.1021/acs.nanolett.4c02853 ↗
28. Xu, X., Gabor, N. M., Alden, J. S., van der Zande, A. M. & McEuen, P. L. Photo-thermoelectric effect at a graphene interface junction. Nano Lett. 10, 562–566 (2010).10.1021/nl903451y ↗
29. Candussio, S. et al. Edge photocurrent driven by terahertz electric field in bilayer graphene. Phys. Rev. B 102, 45406 (2020).10.1103/PhysRevB.102.045406 ↗
30. Castilla, S. et al. Fast and sensitive terahertz detection using an antenna-integrated graphene pn junction. Nano Lett. 19, 2765–2773 (2019).10.1021/acs.nanolett.8b04171 ↗
31. Semkin, V. A. et al. Zero-bias photodetection in 2D materials via geometric design of contacts. Nano Lett. 23, 5250–5256 (2023).10.1021/acs.nanolett.3c01259 ↗
32. Sinha, S. et al. Berry curvature dipole senses topological transition in a moiré superlattice. Nat. Phys. 18, 765–770 (2022).10.1038/s41567-022-01606-y ↗
33. He, P. et al. Graphene moiré superlattices with giant quantum nonlinearity of chiral Bloch electrons. Nat. Nanotechnol. 17, 378–383 (2022).10.1038/s41565-021-01060-6 ↗
34. Guinea, F. & Walet, N. R. Electrostatic effects, band distortions, and superconductivity in twisted graphene bilayers. Proc. Natl Acad. Sci. USA 115, 13174–13179 (2018).10.1073/pnas.1810947115 ↗
35. Ma, C. et al. Moiré band topology in twisted bilayer graphene. Nano Lett. 20, 6076–6083 (2020).10.1021/acs.nanolett.0c02131 ↗
36. Jiang, Y. et al. Charge order and broken rotational symmetry in magic-angle twisted bilayer graphene. Nature 573, 91–95 (2019).10.1038/s41586-019-1460-4 ↗
37. Nuckolls, K. P. et al. Quantum textures of the many-body wavefunctions in magic-angle graphene. Nature 620, 525–532 (2023).10.1038/s41586-023-06226-x ↗
38. Long, M. et al. An atomistic approach for the structural and electronic properties of twisted bilayer graphene-boron nitride heterostructures. npj Comput. Mater. 8, 73 (2022).10.1038/s41524-022-00763-1 ↗
39. Song, J. C. W., Shytov, A. V. & Levitov, L. S. Electron interactions and gap opening in graphene superlattices. Phys. Rev. Lett. 111, 266801 (2013).10.1103/PhysRevLett.111.266801 ↗
40. Jiang, J. et al. Flexo-photovoltaic effect in MoS2. Nat. Nanotechnol. 16, 894–901 (2021).10.1038/s41565-021-00919-y ↗
41. Zhu, M. J. et al. Edge currents shunt the insulating bulk in gapped graphene. Nat. Commun. 8, 14552 (2017).
42. Uri, A. et al. Mapping the twist-angle disorder and Landau levels in magic-angle graphene. Nature 581, 47–52 (2020).10.1038/s41586-020-2255-3 ↗
43. Hesp, N. C. H. et al. Cryogenic nano-imaging of second-order moiré superlattices. Nat. Mater. 23, 1664–1670 (2024).10.1038/s41563-024-01993-y ↗
44. Choi, Y. et al. Correlation-driven topological phases in magic-angle twisted bilayer graphene. Nature 589, 536–541 (2021).10.1038/s41586-020-03159-7 ↗
45. Kwan, Y. H. et al. Kekulé spiral order at all nonzero integer fillings in twisted bilayer graphene. Phys. Rev. X 11, 41063 (2021).
46. Lian, B. et al. Twisted bilayer graphene. IV. Exact insulator ground states and phase diagram. Phys. Rev. B 103, 205414 (2021).10.1103/PhysRevB.103.205414 ↗
47. Kim, H. et al. Imaging inter-valley coherent order in magic-angle twisted trilayer graphene. Nature 623, 942–948 (2023).10.1038/s41586-023-06663-8 ↗
48. Song, Z.-D. & Bernevig, B. A. Magic-angle twisted bilayer graphene as a topological heavy fermion problem. Phys. Rev. Lett. 129, 47601 (2022).10.1103/PhysRevLett.129.047601 ↗
49. Datta, A., Calderón, M. J., Camjayi, A. & Bascones, E. Heavy quasiparticles and cascades without symmetry breaking in twisted bilayer graphene. Nat. Commun. 14, 5036 (2023).
50. Tian, H. et al. Evidence for Dirac flat band superconductivity enabled by quantum geometry. Nature 614, 440–444 (2023).10.1038/s41586-022-05576-2 ↗
51. Bandurin, D. A. et al. Resonant terahertz detection using graphene plasmons. Nat. Commun. 9, 5392 (2018).10.1038/s41467-018-07848-w ↗
52. Khalaf, E., Kruchkov, A. J., Tarnopolsky, G. & Vishwanath, A. Magic angle hierarchy in twisted graphene multilayers. Phys. Rev. B 100, 085109 (2019).10.1103/PhysRevB.100.085109 ↗
53. Park, J. M. et al. Robust superconductivity in magic-angle multilayer graphene family. Nat. Mater. 21, 877–883 (2022).10.1038/s41563-022-01287-1 ↗
54. Purdie, D. G. et al. Cleaning interfaces in layered materials heterostructures. Nat. Commun. 9, 5387 (2018).10.1038/s41467-018-07558-3 ↗
55. Cao, Y. et al. Superlattice-induced insulating states and valley-protected orbits in twisted bilayer graphene. Phys. Rev. Lett. 117, 116804 (2016).10.1103/PhysRevLett.117.116804 ↗
56. Krishna Kumar, R. Data for main text figs—terahertz photocurrent probe of quantum geometry and interactions in magic-angle twisted bilayer graphene. Zenodo https://doi.org/10.5281/zenodo.14882592 (2025).10.5281/zenodo.14882592 ↗