Supercurrent in Bi$_4$Te$_3$ Topological Material-Based Three-Terminal Junctions

TL;DR

This study investigates the transport properties of a three-terminal Josephson junction made from topological insulator Bi$_4$Te$_3$ and superconductor Nb, revealing supercurrent coupling, Shapiro steps, and interference patterns.

Contribution

It provides new insights into the supercurrent behavior and coupling effects in topological insulator-based Josephson junctions through experimental and numerical analysis.

Findings

Extended Josephson supercurrent regions observed

Presence of fractional Shapiro steps indicating skewed current-phase relationship

Fraunhofer-like interference patterns in magnetic field

Abstract

In an in-situ prepared three-terminal Josephson junction based on the topological insulator Bi$_4$Te$_3$ and the superconductor Nb the transport properties are studied. The differential resistance maps as a function of two bias currents reveal extended areas of Josephson supercurrent including coupling effects between adjacent superconducting electrodes. The observed dynamics for the coupling of the junctions is interpreted using a numerical simulation of a similar geometry based on a resistively and capacitively shunted Josephson junction model. The temperature dependency indicates that the device behaves similar to prior experiments with single Josephson junctions comprising topological insulators weak links. Irradiating radio frequencies to the junction we find a spectrum of integer Shapiro steps and an additional fractional step, which is interpreted by a skewed current-phase relationship. In a perpendicular magnetic field we observe Fraunhofer-like interference patterns of the switching currents.