Cascades between Light and Heavy Fermions in the Normal State of Magic-Angle Twisted Bilayer Graphene

Jian Kang, B. Andrei Bernevig, Oskar Vafek

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

We present a framework for understanding the cascade transitions and the Landau level degeneracies of twisted bilayer graphene. The Coulomb interaction projected onto narrow bands causes the charged excitations at an integer filling to disperse, forming new bands. If the excitation moves the filling away from the charge neutrality point, then it has a band minimum at the moiré Brillouin zone center with a small mass that compares well with the experiment; if towards the charge neutrality point, then it has a much larger mass and a higher degeneracy. At a nonzero density away from an integer filling the excitations interact. The system on the small mass side has a large bandwidth and forms a Fermi liquid. On the large mass side the bandwidth is narrow, the compressibility is negative and the Fermi liquid is likely unstable. This explains the observed sawtooth features in compressibility, the Landau fans pointing away from charge neutrality and their degeneracies. The framework sets the stage for superconductivity at lower temperatures.

Original languageEnglish (US)
Article number266402
JournalPhysical review letters
Volume127
Issue number26
DOIs
StatePublished - Dec 24 2021

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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