# Nodal surface and persistent spin texture in a Weyl semimetal without mirror symmetry

## TL;DR

This study uncovers a nodal plane and unique spin textures in a Weyl semimetal without mirror symmetry, highlighting its potential for novel chiral anomaly phenomena and spintronic applications.

## Contribution

It reveals the existence of a nodal plane, Weyl points, and spin textures in Ag$_{2}$Se, demonstrating features absent in systems with mirror symmetry and suggesting new physical phenomena.

## Key findings

- Discovered a nodal plane at $k_{z}= ext{pi}$ protected by symmetry.
- Identified 24 Weyl points with Fermi arcs and notable QPI patterns.
- Revealed direction-selective spin polarization on the surface.

## Abstract

By utilizing symmetry analysis and electronic structure calculations, we investigated the low-temperature orthorhombic phase of Ag$_{2}$Se in ${\cal SG}$~17. In addition to the discovery of a nodal plane at $k_{z}=\pi$ protected by the joint operation of time-reversal (${\cal T}$) and the 2-fold screw rotation $S_{2z}$, we found 24 Weyl points mainly residing at the $k_{y}=0$ plane with notable Fermi arc and large quasiparticle interference pattern (QPI). Due to the absence of mirror symmetry, a pair of Weyl points with opposite chirality reside at different binding energies, which makes this system an excellent material candidate for realizing the novel chiral anomaly related phenomenon, such as the quantized circular photogalvanic and the chiral magnetic effects. Furthermore, we also reveal the striking spin textures at $k_{z}=\pi$ plane which demonstrates, in a large region of the surface Brillouin Zone, a direction-selective spin polarization, which has a strong implication to spintronic applications.