Most existing approaches to realize the superconducting diode effect rely on breaking time-reversal symmetry, often through an external magnetic field or magnetic materials, which limits the device integration.

In a study published in Physical Review X, a team led by Prof. ZHENG Guolin from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences realized a superconducting diode effect in a device that preserves time-reversal symmetry in NbSe₂ homojunctions under zero magnetic field.

Researchers tuned the carrier concentration and carrier type in NbSe₂, fabricating n-n, p-n, and p-p superconducting homojunctions. In the devices, all three types of junctions exhibited clear diode-like behavior, allowing supercurrent to flow more easily in one direction than the other, even in the absence of an applied magnetic field.

The direction of the diode effect depended on the type of junction: n-n devices showed an opposite polarity compared with p-n and p-p structures. Measurements also showed that the asymmetry remained unchanged under magnetic field variations, confirming that time-reversal symmetry was not broken.

Researchers attribute the effect to the movement of protons at the junction under an applied current, which influences the transition between superconducting and resistive states under opposite bias directions.

This study provides a new route to design superconducting diode devices without relying on time-reversal symmetry breaking.