Cascade of transitions in twisted and non-twisted graphene layers within the van Hove scenario

Dmitry V. Chichinadze, Laura Classen, Yuxuan Wang, Andrey V. Chubukov

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4 Scopus citations

Abstract

Motivated by measurements of compressibility and STM spectra in twisted bilayer graphene, we analyze the pattern of symmetry breaking for itinerant fermions near a van Hove singularity. Making use of an approximate SU(4) symmetry of the Landau functional, we show that the structure of the spin/isospin order parameter changes with increasing filling via a cascade of transitions. We compute the feedback from different spin/isospin orders on fermions and argue that each order splits the initially 4-fold degenerate van Hove peak in a particular fashion, consistent with the STM data and compressibility measurements, providing a unified interpretation of the cascade of transitions in twisted bilayer graphene. Our results follow from a generic analysis of an SU(4)-symmetric Landau functional and are valid beyond a specific underlying fermionic model. We argue that an analogous van Hove scenario explains the cascade of phase transitions in non-twisted Bernal bilayer and rhombohedral trilayer graphene.

Original languageEnglish
Article number114
Journalnpj Quantum Materials
Volume7
Issue number1
DOIs
StatePublished - Dec 2022
Externally publishedYes

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