Simultaneously improving Rashba-type and Zeeman effects in two-dimensional multiferroics

Abstract

First-principles calculations are performed to investigate Rashba-type and Zeeman effects in two-dimensional three-atom-layer structures $X\mathrm{Te}$/MnTe/$X\mathrm{Te}$ ($XMX, X=\text{Sn}$, Ge). It is found that the Rashba-type and Zeeman effects that typically compete against each other rather cooperatively work together and are improved in $XMX$, as compared to $X\mathrm{Te}/X\mathrm{Te}/X\mathrm{Te}$ ($XXX$). This cooperation and improvement are highly required in Majorana qubits for topological quantum computing, Josephson junction of topological superconductivity, and other phenomena. The Rashba-type effect is improved because replacing $X\mathrm{Te}$ by MnTe leads to a reduction of the thickness of $XMX$ and increases the interaction between the surface state of the lowest conduction bands and its neighboring states. The improved Zeeman effect in the $XMX$ structure arises from s-d and p-d exchange interactions between Te and Mn ions. The present strategy of simultaneously largely improving Rashba-type and Zeeman effects therefore provides a route to realize stable Majorana fermions, topological superconductivity, and other phenomena that require both large Rashba-type and Zeeman effects.