Highly tunable junctions in magic-angle graphene tunnelling devices

Magic-angle twisted bilayer graphene (MATBG) and related systems have recently emerged as highly tunable two-dimensional material platforms exhibiting a wide range of phases, such as metal, insulator and superconductor states. Local electrostatic control over these phases may enable the creation of versatile quantum devices that were previously not achievable in other single-material platforms. In this talk, I will expand on our recent results in MATBG [1], where we show Josephson junctions and tunnelling transistors in twisted graphene devices, solely defined by electrostatic gates. Our multi-gated device geometry offers independent control of the weak link, barriers and tunnelling electrodes. Utilizing the intrinsic bandgaps of MATBG, we also demonstrate monolithic edge tunnelling spectroscopy within the same MATBG devices and measure the energy spectrum of MATBG in the superconducting phase. Furthermore, by inducing a double-barrier geometry, the devices can be operated as a single-electron transistor, exhibiting Coulomb blockade. With versatile functionality encompassed within a single material, these tunnelling devices may find applications in graphene-based tunable superconducting qubits, on-chip superconducting circuits and electromagnetic sensing. 

 

[1] Rodan-Legrain, D. et al. Highly tunable junctions and non-local Josephson effect in magic-angle graphene tunnelling devices. Nature Nanotechnology 16, 769–775 (2021).