Strain Disorder and Gapless Intervalley Coherent Phase in Twisted Bilayer Graphene

Abstract

Correlated insulators are frequently observed in magic angle twisted bilayer graphene at even fillings of electrons or holes per moiré unit-cell. Whereas theory predicts these insulators to be intervalley coherent excitonic phases, the measured gaps are routinely much smaller than theoretical estimates. We explore the effects of random strain variations on the intervalley coherent phase, which have a pair-breaking effect analogous to magnetic disorder in superconductors. We find that the spectral gap may be strongly suppressed by strain disorder, or vanish altogether, even as intervalley coherence is maintained. We discuss predicted features of the tunneling density of states, show that the activation gap measured in transport experiments corresponds to the diminished gap, and thus offer a solution for the apparent discrepancy between the theoretical and experimental gaps.

5 pages, 4 figures + Supplementary. Published version

References in corpus (4)

• Lattice relaxation and energy band modulation in twisted bilayer graphenes
• Global Phase Diagram of the Normal State of Twisted Bilayer Graphene
• Theory of correlated insulators and superconductivity in twisted bilayer graphene
• Influence of Disorder on Electron-Hole Pair Condensation in Graphene Bilayers

Cited by in corpus (6)

• Emergent correlated phases in rhombohedral trilayer graphene induced by proximity spin-orbit and exchange coupling
• Inducing superconductivity in bilayer graphene by alleviation of the Stoner blockade
• Weak Coupling Theory of Magic-Angle Twisted Bilayer Graphene
• Dimensional reduction from magnetic field in moiré superlattices
• Correlated phases in rhombohedral multilayer graphene
• Correlated Insulator Moiré Bolometer