Hexagonal Zr3X (X = Al, Ga, In) Metals: High Dynamic Stability, Nodal Loop, and Perfect Nodal Surface States.

Heju Xu,Yong-Chun Gao,Hailong Xi

doi:10.3389/fchem.2020.608398

Heju Xu, Yong-Chun Gao + Show 1 more

Open Access

https://doi.org/10.3389/fchem.2020.608398

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Abstract

In recent years, topological semimetals/metals, including nodal point, nodal line, and nodal surface semimetals/metals, have been studied extensively because of their potential applications in spintronics and quantum computers. In this study, we predict a family of materials, Zr3X (X = Al, Ga, In), hosting the nodal loop and nodal surface states in the absence of spin–orbit coupling. Remarkably, the energy variation of the nodal loop and nodal surface states in Zr3X are very small, and these topological signatures lie very close to the Fermi level. When the effect of spin–orbit coupling is considered, the nodal loop and nodal surface states exhibit small energy gaps (<25 and 35 meV, respectively) that are suitable observables that reflect the spin-orbit coupling response of these topological signatures and can be detected in experiments. Moreover, these compounds are dynamically stable, and they consequently form potential material platforms to study nodal loop and nodal surface semimetals.

Highlights

The exploration of non-trivial topologies in crystalline solids has attracted significant attention from chemists, physicists, and material scientists (Kong and Cui, 2011; Cava et al, 2013; Banik et al, 2018; Zhang et al, 2018a; Tang et al, 2019)
Neglecting spin-orbit coupling, there is a nodal loop in the kz = 0 plane and nodal surface state in the kz = π plane
It is expected that these non-trivial band-crossings can be experimentally observed via angle-resolved photoemission spectroscopy (ARPES)

Summary

Introduction

The exploration of non-trivial topologies in crystalline solids has attracted significant attention from chemists, physicists, and material scientists (Kong and Cui, 2011; Cava et al, 2013; Banik et al, 2018; Zhang et al, 2018a; Tang et al, 2019). Hexagonal Zr3X Metals (Peng et al, 2016; Lin et al, 2017; Fu et al, 2018; Zhang et al, 2018c; Zhou et al, 2019; Gupta et al, 2020; Jia et al, 2020; Liu et al, 2020; Meng L. et al, 2020; Zhao B. et al, 2020). We selected Weyl semimetals/metals as examples here because there exists a band-crossing of the valance band and conduction band at an isolated nodal point in the momentum space of these solids. Around this isolated nodal point, the quasiparticle acts to the behavior of Weyl fermions, which are particles of considerable interest in high-energy physics. Under the protection from certain crystalline symmetries, two Weyl points of opposite chirality can be stable at the same point, forming a Dirac point

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