Zero-field superconducting diode effect induced by magnetic flux in a van der Waals superconductor trigonal PtBi$_2$

TL;DR

This paper demonstrates a zero-field superconducting diode effect in trigonal PtBi₂, controlled by trapped magnetic flux, revealing a new way to achieve nonreciprocal superconducting transport without external magnetic fields.

Contribution

The study shows that trapped magnetic flux can induce and control the superconducting diode effect in a van der Waals superconductor, enabling zero-field operation.

Findings

Superconducting diode effect observed at zero external magnetic field.

Sign of the diode effect controlled by prior magnetic poling.

Trapped magnetic flux responsible for breaking time-reversal symmetry.

Abstract

The superconducting diode effect is one of the nonreciprocal transport phenomena, where the critical current depends on the current direction. This effect is typically realized in superconductors with broken spatial-inversion and time-reversal symmetry. To break the time-reversal symmetry, external magnetic fields are commonly used. Here, we demonstrate a sign-controllable superconducting diode effect under zero external magnetic field in a van der Waals superconductor trigonal PtBi$_2$. The sign of the zero-field superconducting diode effect is controlled by the poling magnetic field, that is a large magnetic field applied prior to measurements. This result indicates that trapped magnetic flux are responsible for breaking the time-reversal symmetry. Our findings highlight the crucial role of trapped magnetic flux in generating the superconducting diode effect and provide a general pathway for realizing a zero-field superconducting diode effect.