Tuning superconductivity in twisted bilayer graphene

TL;DR

This paper shows how adjusting interlayer coupling in twisted bilayer graphene, via pressure, can tune superconductivity and correlated phases beyond the standard magic angle, enhancing its potential for exploring quantum phenomena.

Contribution

It introduces a method to tune superconductivity in twisted bilayer graphene by modifying interlayer coupling, expanding control beyond the twist angle alone.

Findings

Superconductivity can be induced at twist angles larger than 1.1° by varying interlayer spacing.

Hydrostatic pressure enables tuning of correlated phases in twisted bilayer graphene.

Low-disorder devices reveal detailed phase diagrams and relationships between phases.

Abstract

Materials with flat electronic bands often exhibit exotic quantum phenomena owing to strong correlations. Remarkably, an isolated low-energy flat band can be induced in bilayer graphene by simply rotating the layers to 1.1$^{\circ}$, resulting in the appearance of gate-tunable superconducting and correlated insulating phases. Here, we demonstrate that in addition to the twist angle, the interlayer coupling can also be modified to precisely tune these phases. We establish the capability to induce superconductivity at a twist angle larger than 1.1$^{\circ}$ $-$ in which correlated phases are otherwise absent $-$ by varying the interlayer spacing with hydrostatic pressure. Realizing devices with low disorder additionally reveals new details about the superconducting phase diagram and its relationship to the nearby insulator. Our results demonstrate twisted bilayer graphene to be a uniquely tunable platform for exploring novel correlated states.