# Symmetry-assisted protection and compensation of hidden spin polarization in centrosymmetric systems

## TL;DR

This paper proposes a symmetry-based method to protect and enhance hidden spin polarization in centrosymmetric materials, enabling potential applications in topological superconductivity.

## Contribution

It introduces a nonsymmorphic symmetry approach to safeguard HSP and identifies hundreds of candidate materials, including rare-earth compounds, for experimental exploration.

## Key findings

- Protection of strong sector-projected spin textures via nonsymmorphic symmetry.
- Identification of 17 layer groups supporting symmetry-assisted HSP.
- Hundreds of candidate materials, including LnOI compounds, exhibiting strong HSP.

## Abstract

It is recently noted that in certain centrosymmetric compounds, spin-orbit interaction couples each local sector that lacks inversion symmetry and thus leads to visible spin polarization effects in the real space, dubbed as 'hidden spin polarization (HSP)'. However, observable spin polarization of a given local sector suffers interference by its inversion partner, impeding material realization and potential applications of HSP. Starting from a single-orbital tight-binding model, we propose a nontrivial way to protect strong sector-projected spin texture through minimizing the interaction between inversion partners by nonsymmorphic symmetry. The HSP effect is generally compensated by inversion partners near the {\Gamma} point but immune from interaction around the boundary of the Brillouin zone. We further summarize 17 layer groups that support such symmetry-assisted HSP and identify by first-principle calculations hundreds of quasi-2D materials from the existing databases, among which a group of rare-earth compounds LnOI (Ln = Pr, Nd, Ho, Tm and Lu) serves as great candidates showing strong Rashba- and Dresselhaus-type HSP. Our finding also provides an ideal platform to control HSP for emergent physical effects, such as opening a hybridization gap by tensile strain to realize the time-reversal-invariant topological superconductivity.

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Source: https://tomesphere.com/paper/1902.10277