Charge-Order and Broken Rotational Symmetry in Magic Angle Twisted Bilayer Graphene

TL;DR

This study uses STM/STS to visualize charge order and symmetry breaking in magic angle twisted bilayer graphene, revealing a pseudogap phase and stripe charge order that connect to high-temperature superconductor phenomena.

Contribution

It provides direct local spectroscopic evidence of charge order and broken rotational symmetry in TBLG, linking these features to correlated electronic phases.

Findings

Observation of a pseudogap phase in TBLG

Detection of stripe charge order in the material

Evidence of broken rotational symmetry

Abstract

The discovery of correlated electronic phases, including Mott-like insulators and superconductivity, in twisted bilayer graphene (TBLG) near the magic angle, and the intriguing similarity of their phenomenology to that of the high-temperature superconductors, has spurred a surge of research to uncover the underlying physical mechanism. Local spectroscopy, which is capable of accessing the symmetry and spatial distribution of the spectral function, can provide essential clues towards unraveling this puzzle. Here we use scanning tunneling microscopy (STM) and spectroscopy (STS) in magic angle TBLG to visualize the local density of states (DOS) and charge distribution. Doping the sample to partially fill the flat band, where low temperature transport measurements revealed the emergence of correlated electronic phases, we find a pseudogap phase accompanied by a global stripe charge-order whose similarity to high-temperature superconductors provides new evidence of a deeper link underlying the phenomenology of these systems.