Broken-symmetry states at half-integer band fillings in twisted bilayer graphene

Saisab Bhowmik, Bhaskar Ghawri, Nicolas Leconte, Samudrala Appalakondaiah, Mrityunjay Pandey, Phanibhusan S. Mahapatra, Dongkyu Lee, K. Watanabe, T. Taniguchi, Jeil Jung, Arindam Ghosh, U. Chandni

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

The dominance of Coulomb interactions over the kinetic energy of electrons in flat moiré bands of magic-angle twisted bilayer graphene (TBG) gives rise to a variety of correlated phases, including correlated insulators1–3, superconductivity2,4,5, orbital ferromagnetism2,6, Chern insulators7–10 and nematicity11. Most of these phases occur when the carrier density is at or near an integer number of carriers per moiré unit cell. However, the demonstration of ordered states at fractional moiré band fillings at zero applied magnetic field is more challenging. Here we report the observation of states near half-integer band fillings 0.5 and ±3.5 at near-zero magnetic field in TBG proximitized by tungsten diselenide. Furthermore, at a band filling near −0.5, a symmetry-broken Chern insulator emerges at high magnetic field that is compatible with the band structure calculations within a translational symmetry-broken supercell with twice the area of the original TBG moiré cell. Our results are consistent with a spin or charge density wave ground state in TBG in the zero-magnetic-field limit.

Original languageEnglish
Pages (from-to)639-643
Number of pages5
JournalNature Physics
Volume18
Issue number6
DOIs
StatePublished - Jun 2022

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