Topological node line semimetal state in two-dimensional tetragonal allotrope of Ge and Sn. (15th March 2019)

• Record Type: Journal Article
• Authors: Xu, Chunyan; Wang, Yanjie; Han, Ruilin; Tu, Haoran; Yan, Yu
• Is Part Of: New journal of physics. Volume 21:Number 3(2019:Mar.)
• Publication Date: 2019-03-15
• Subjects: two-dimensional material -- first-principles calculations -- node line semimetal -- strain; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/ab0457
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: Realizing semimetal states in two-dimensional (2D) materials are of great importance for their future application in novel quantum devices at the nanoscale. Using first-principles calculations based on density functional theory, we propose a new 2D tetragonal allotrope of Ge and Sn, 2D T-Ge and T-Sn, which consists of repeated square and octagon rings. The calculated cohesive energy, ab initio molecular dynamic simulations and phonon dispersions indicate that 2D T-Ge and T-Sn are stable at room temperature and possibly synthesized in the experiments under appropriate growth conditions. In the absence of spin–orbital coupling (SOC), 2D T-Ge and T-Sn are node line semimetals and the nodal loop in 2D T-Ge and T-Sn are protected by the combination of the spatial inversion P and time-reversal T symmetries. Remarkably, when SOC is included, 2D T-Ge and T-Sn are still node line semimetals although small gap is opened along the nodal loop, which are identified by nontrivialZ 2 invariant and topological edge states at the sample boundaries. Furthermore, our calculations show that node line semimetal states in 2D T-Ge and T-Sn are robust with the biaxial strains in the range of −3% to 3%. Our results provide a new 2D material platform for realization of 2D topological node line semimetals and innovative applications of topological node line semimetals.