Observation of flat bands in gated semiconductor artificial graphene

TL;DR

This paper reports the experimental observation of flat bands in semiconductor artificial graphene using GaAs quantum well transistors, revealing flat band features and their interaction with electron density.

Contribution

It provides the first evidence of flat bands in semiconductor artificial graphene through photoluminescence spectra, demonstrating tunability and stability near the Fermi level.

Findings

Observation of van Hove singularity doublet in AG

Flat bands accessible to the Fermi level

Spectral stability indicating electron interactions

Abstract

Flat bands near M points in the Brillouin zone are key features of honeycomb symmetry in artificial graphene (AG) where electrons may condense into novel correlated phases. Here we report the observation of van Hove singularity doublet of AG in GaAs quantum well transistors, which presents the evidence of flat bands in semiconductor AG. Two emerging peaks in photoluminescence spectra tuned by backgate voltages probe the singularity doublet of AG flat bands, and demonstrate their accessibility to the Fermi level. As the Fermi level crosses the doublet, the spectra display dramatic stability against electron density, indicating interplays between electron-electron interactions and honeycomb symmetry. Our results provide a new flexible platform to explore intriguing flat band physics.