Gate-defined single-electron transistors in twisted bilayer graphene

TL;DR

This paper demonstrates gate-defined single-electron transistors in twisted bilayer graphene near the magic angle, enabling exploration of strong correlations, band renormalisation, and quantum oscillations in a highly tunable platform.

Contribution

It introduces gate-controlled SETs in tBLG, revealing new insights into electronic phases and Fermi surface tunability related to strong correlations and band structure.

Findings

Gate-defined SETs in tBLG show Coulomb blockade resonances.

Quantum oscillations reveal gate-tunable Fermi surfaces.

Displacement-field-induced band renormalisation is crucial for device control.

Abstract

Twisted bilayer graphene (tBLG) near the magic angle is a unique platform where the combination of topology and strong correlations gives rise to exotic electronic phases. These phases are gate-tunable and related to the presence of flat electronic bands, isolated by single-particle band gaps. This enables gate-controlled charge confinement, essential for the operation of single-electron transistors (SETs), and allows to explore the interplay of confinement, electron interactions, band renormalisation and the moir\'e superlattice, potentially revealing key paradigms of strong correlations. Here, we present gate-defined SETs in near-magic-angle tBLG with well-tunable Coulomb blockade resonances. These SETs allow to study magnetic field-induced quantum oscillations in the density of states of the source-drain reservoirs, providing insight into gate-tunable Fermi surfaces of tBLG. Comparison with tight-binding calculations highlights the importance of displacement-field-induced band renormalisation crucial for future advanced gate-tunable quantum devices and circuits in tBLG including e.g. quantum dots and Josephson junction arrays.