Twist-angle tunable Josephson junctions in three-dimensional superconductors

TL;DR

This paper presents a theoretical study of twist-angle tunable Josephson junctions in 3D superconductors, showing how the supercurrent can be controlled by the twist angle, with potential applications in quantum devices.

Contribution

It introduces a self-consistent framework for analyzing superconducting phase and supercurrent in twisted 3D superconductors, revealing twist-controlled Josephson effects.

Findings

Finite critical current exists even with separated Fermi surfaces.

Critical current varies with twist angle, enabling tunability.

Phase discontinuity indicates twist-induced Josephson junction formation.

Abstract

We theoretically investigate the superconducting phase and perpendicular Josephson supercurrent in twisted three-dimensional (3D) superconductors, where two layered 3D materials are stacked with a relative twist. We formulate the Bogoliubov-de Gennes Hamiltonian and develop a self-consistent method to calculate the superconducting order parameter and the resulting supercurrent. Applying this framework to a toy model with Fermi surfaces located near the Brillouin zone corners, we demonstrate a phase discontinuity at the twisted interface, indicating that a Josephson junction is formed purely by the twist. Our calculations reveal that the interface supports a finite critical current even when the Fermi surfaces of the two superconductors are completely separated, unlike in the case of a twisted normal-metal interface. We further show that the critical current can be effectively controlled by the twist angle, transitioning from a high-transparency regime at small angles to a low-transparency regime at larger angles.