SU(4) symmetry breaking revealed by magneto-optical spectroscopy in epitaxial graphene

TL;DR

This study uses magneto-optical spectroscopy to detect SU(4) symmetry breaking in multilayer epitaxial graphene, revealing a charge density wave as the underlying cause at high magnetic fields.

Contribution

It provides the first experimental evidence of SU(4) symmetry breaking in graphene's Landau levels due to a charge density wave.

Findings

Observation of a new absorption transition at B>26 T

Identification of charge density wave as the symmetry-breaking mechanism

Quantitative model matching experimental data

Abstract

Refined infrared magnetotransmission experiments have been performed in magnetic fields B up to 35 T on a series of multilayer epitaxial graphene samples. Following the main optical transition involving the n=0 Landau level (LL), we observe a new absorption transition increasing in intensity with magnetic fields B>26 T. Our analysis shows that this is a signature of the breaking of the SU(4) symmetry of the n=0 LL. Using a quantitative model, we show that the only symmetry-breaking scheme consistent with our experiments is a charge density wave (CDW).