CaFeAs$_2$: a Staggered Intercalation of Quantum Spin Hall and High Temperature Superconductivity

TL;DR

This paper predicts that CaFeAs$_2$ is a novel staggered intercalation compound combining topological quantum spin Hall insulators and high-temperature superconductivity, opening avenues for exploring Majorana modes.

Contribution

It introduces CaFeAs$_2$ as a new material integrating topological QSH and superconductivity layers, revealing potential for novel quantum physics phenomena.

Findings

CaFeAs$_2$ has staggered CaAs and FeAs layers.

CaAs layers are Z2 topological QSH insulators.

Bulk is a 3D weak topological insulator.

Abstract

We predict that CaFeAs$_2$, a newly discovered iron-based high temperature (T$_c$) superconductor, is a staggered intercalation compound that integrates topological quantum spin hall (QSH) and superconductivity (SC). CaFeAs$_2$ has a structure with staggered CaAs and FeAs layers. While the FeAs layers are known to be responsible for high T$_c$ superconductivity, we show that with spin orbital coupling each CaAs layer is a $Z_{2}$ topologically nontrivial two-dimensional QSH insulator and the bulk is a 3-dimensional weak topological insulator. In the superconducting state, the edge states in the CaAs layer are natural 1D topological superconductors. The staggered intercalation of QSH and SC provides us an unique opportunity to realize and explore novel physics, such as Majorana modes and Majorana Fermions chains.