Cubic Hafnium Nitride: A Novel Topological Semimetal Hosting a 0-Dimensional (0-D) Nodal Point and a 1-D Topological Nodal Ring.

Yang Li,Jihong Xia

doi:10.3389/fchem.2020.00727

Abstract

Very recently, topological semimetals with nontrivial band crossing and associated topological surface states have received widespread attention. Various types of topological semimetals, including nodal point semimetals, nodal line semimetals, and nodal surface semimetals, have been predicted from first principles. In absence of spin-orbit coupling (SOC) effect, we propose that cubic-type hafnium nitride (HfN) with a space group is a novel topological semimetal hosting a rare 0-D triple nodal point and a 1-D topological nodal ring. More importantly, the interesting 0-D and 1-D topological states all occur near the Fermi level, and these topological states are not disturbed by other extraneous bands. When the SOC effect is taken into consideration, 0-D triple nodal point was gapped and a new 0-D topological element, namely, Dirac point appears along Γ-R path. Finally, the dynamical and mechanical stabilities of this semimetal and its associated mechanical properties are discussed in order to provide a reference for future investigations. Our work promises that HfN can serve as a superior topological semimetal with high stability, excellent mechanical properties, and rich topological states.

Highlights

After the discovery of topological insulators (Zhang et al, 2009; Hasan and Kane, 2010; Yu et al, 2010; Qi and Zhang, 2011; Rechtsman et al, 2013), topological semimetals (Jiang et al, 2015; Fang et al, 2016; Chang et al, 2017; Yan and Felser, 2017; Gao et al, 2019) with topological band inversion and exotic topological boundary states have attracted widespread attention
In addition to the Weyl and Dirac semimetals generated by twofold- or quadruple-degenerate nodal points, topological nodal point semimetals with triple-degenerate 0-D nodal points have become a new focus of research due to their novel topological states and related physics properties
Based on the 3-D Brillouin zone (BZ), the phonon dispersion was determined in order to examine the dynamical stability of cubic hafnium nitride (HfN) material with this space group

Summary

Introduction

After the discovery of topological insulators (Zhang et al, 2009; Hasan and Kane, 2010; Yu et al, 2010; Qi and Zhang, 2011; Rechtsman et al, 2013), topological semimetals (Jiang et al, 2015; Fang et al, 2016; Chang et al, 2017; Yan and Felser, 2017; Gao et al, 2019) with topological band inversion and exotic topological boundary states have attracted widespread attention. Topological nodal line semimetals (Cai et al, 2018; Chen et al, 2018; Zhou et al, 2018; Pham et al, 2019; Yi et al, 2019) possess 1-D topological elements, which are formed by band crossing along a line in momentum space. Topological nodal ring semimetals have emerged as a hot research topic very recently because these topological materials have intriguing electronic band behaviors and interesting drum-head-like surface states.

Results

Conclusion