Dirac cone spectroscopy of strongly correlated phases in twisted trilayer graphene

TL;DR

This paper introduces a novel spectroscopy technique to study correlated quantum phases in mirror-symmetric twisted trilayer graphene, revealing energy gaps, Chern numbers, and phase transitions that deepen understanding of strong correlations in moire systems.

Contribution

The work presents a new spectroscopy method to quantify energy gaps and topological properties of correlated states in twisted trilayer graphene, uncovering novel phases and phase transitions.

Findings

Identified hard correlated gaps with Chern number C=0 at fillings nu=2 and 3.

Discovered charge density wave states at fractional fillings nu=5/3 and 11/3.

Observed displacement field-driven phase transitions at charge neutrality and half fillings.

Abstract

Mirror-symmetric magic-angle twisted trilayer graphene (MATTG) hosts flat electronic bands close to zero energy, and has been recently shown to exhibit abundant correlated quantum phases with flexible electrical tunability. However studying these phases proved challenging as these are obscured by intertwined Dirac bands. In this work, we demonstrate a novel spectroscopy technique, that allows to quantify the energy gaps and Chern numbers of the correlated states in MATTG by driving band crossings between Dirac cone Landau levels and the energy gaps in the flat bands. We uncover hard correlated gaps with Chern numbers of C = 0 at integer moire unit cell fillings of nu = 2 and 3 and reveal novel charge density wave states originating from van Hove singularities at fractional fillings of nu = 5/3 and 11/3. In addition, we demonstrate the existence of displacement field driven first-order phase transitions at charge neutrality and half fillings of the moire unit cell nu = 2, which is consistent with a theoretical strong-coupling analysis, implying the breaking of the C2T symmetry. Overall these properties establish the diverse and electrically tunable phase diagram of MATTG and provide an avenue for investigating electronic quantum phases and strong correlations in multiple-band moire systems.