Superconducting Quantum Interference in Twisted van der Waals Heterostructures

Abstract

We demonstrate the formation of both Josephson junctions and superconducting quantum interference devices (SQUIDs) using a dry transfer technique to stack and deterministically misalign mechanically exfoliated flakes of NbSe₂. The current-voltage characteristics of the resulting twisted NbSe₂-NbSe₂ junctions are found to be sensitive to the misalignment angle of the crystallographic axes, opening up a new control parameter for optimization of the device performance, which is not available in thin-film-deposited junctions. A single lithographic process has then been implemented to shape Josephson junctions into SQUID geometries with typical loop areas of ∼25 μm² and weak links ∼600 nm wide. At <i>T</i> = 3.75 K in an applied magnetic field, these devices display large stable current and voltage modulation depths of up to Δ<i>I</i>_c ∼ 75% and Δ<i>V</i> ∼ 1.4 mV, respectively.