Prediction of ferroelectric superconductors with reversible superconducting diode effect

TL;DR

This paper predicts that ferroelectric superconductors can exhibit a reversible superconducting diode effect, controllable by electric switching, demonstrated through first-principles calculations on a specific 2D material.

Contribution

It introduces the concept of a ferroelectric reversible superconducting diode effect and predicts its occurrence in 2D ferroelectric superconductors like CuNb$_2$Se$_4$.

Findings

Monolayer CuNb$_2$Se$_4$ is a ferroelectric superconductor.

The diode effect can be reversed by electric switching of ferroelectricity.

The effect is linked to spin-orbit coupling and layer polarization.

Abstract

A noncentrosymmetric superconductor can have a superconducting diode effect, where the critical current in opposite directions is different when time-reversal symmetry is also broken. We theoretically propose that a ferroelectric superconductor with coexisting ferroelectricity and superconductivity can support a ferroelectric reversible superconducting diode effect. Through first-principles calculation, we predict that monolayer CuNb$_2$Se$_4$ (i.e., bilayer NbSe$_2$ intercalated with Cu) is such a ferroelectric superconductor, where ferroelectricity controls the layer polarization as well as the sign of spin-orbit coupling induced spin splittings. Because the nonreciprocal effect of the critical current is proportional to the spin splittings, the superconducting diode effect is reversible upon electric switch of ferroelectricity. While we use CuNb$_2$Se$_4$ as a model system, the predicted effect can appear in a class of two-dimensional superconducting bilayers with ferroelectricity induced by interlayer sliding. Our work opens the door to studying the interplay between superconductivity and ferroelectricity in two-dimensional materials.