# Orbital mixing in few-layer graphene and non-Abelian Berry phase

Source: [Orbital mixing in few-layer graphene and non-Abelian Berry phase](<https://www.sota2.com/research/paper/68fa40431e209131ce8f2316>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-25T02:42:35.455Z

Authors: K. Shizuya

Published: 2021-10-15T12:31:49.000Z

## Abstract

In a magnetic field few-layer graphene supports, at the lowest Landau level, a multiplet of zero-mode levels nearly degenerate in orbitals as well as in spins and valleys. Those pseudo-zero-mode (PZM) levels are generally sensitive to interactions and external perturbations, and have a crossing among themselves or with other higher Landau levels when an external field is swept over a certain range. A close study is made of how such PZM levels evolve when they are gradually brought from empty to filled levels under many-body interactions. It is pointed out that the level spectra generally avoid a crossing via orbital level mixing and that orbital mixing is governed by a non-Abelian Berry phase that derives from an approximate degeneracy and interactions. A look is also taken into evolution/crossing of many-body ground states with increasing external bias in bilayer graphene.

## Recorded benchmark results

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2110.08056>)

[PDF](<https://arxiv.org/pdf/2110.08056.pdf>)