Comprehensive scan for nonmagnetic Weyl semimetals with nonlinear optical response

Qiunan Xu,Yan Sun,Claudia Felser,Yang Zhang,Jeroen Van Den Brink,Klaus Koepernik,Wujun Shi

doi:10.1038/s41524-020-0301-1

Abstract

First-principles calculations have recently been used to develop comprehensive databases of nonmagnetic topological materials that are protected by time-reversal or crystalline symmetry. However, owing to the low symmetry requirement of Weyl points, a symmetry-based approach to identifying topological states cannot be applied to Weyl semimetals (WSMs). To date, WSMs with Weyl points in arbitrary positions are absent from the well-known databases. In this work, we develop an efficient algorithm to search for Weyl points automatically and establish a database of nonmagnetic WSMs with Weyl points near the Fermi level based on the experimental non-centrosymmetric crystal structures in the Inorganic Crystal Structure Database (ICSD). In total, 46 Weyl semimetals were discovered to have nearly clean Fermi surfaces and Weyl points within 300 meV of the Fermi level. Nine of them are chiral structures which may exhibit the quantized circular photogalvanic effect. In addition, the nonlinear optical response is studied and the giant shift current is explored. Besides nonmagnetic WSMs, our powerful tools can also be used in the discovery of magnetic topological materials.

Highlights

The Fermi arc length can be ~15% of the reciprocal lattice vector, which makes it easy to detect by surface detection methods, such as angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM)
The locations of Weyl points in the Brillouin zone shown in Fig. 3b connected with each other by time reversal, C2x and C2y rotation symmetries
Through the band structure along the k-path crossing one pair of Weyl points in Fig. 3d, we find these Weyl points belong to two different classes, the type-I Weyl points with chirality +1 (W1) and the type-II Weyl points with chirality −1 (W2)

Summary

Introduction

Since the discovery of topological insulators[1,2,3,4,5,6,7], topological band theory has been widely applied to solid state materials[8,9,10,11] and leads to the further classification of both insulators[12,13,14,15,16,17,18] and semimetals[19,20,21,22,23,24,25,26,27,28,29] based on the quantum topological invariants. Some comprehensive databases for the symmetry protected nonmagnetic topological states were established by three independent works[30,31,32]. These useful databases contain the topological insulators, and the semimetals with degeneracy points located at high-symmetric lines or points. In these databases, an important category of topological materials, e.g., the Weyl semimetal (WSM) whose degeneracy point can locate at any position in the entire Brillouin zone, is still absent.

Methods

Results

Conclusion