Issue 25, 2017

Dirac node lines in two-dimensional Lieb lattices

Abstract

As a new type of quantum matter, Dirac node line (DNL) semimetals are currently attracting widespread interest in condensed matter physics and materials science. The DNL, featured by a closed line consisting of linear band crossings in the momentum space, was mostly predicted in three-dimensional materials. Here, we propose a tight-binding (TB) model of pz + px,y or pz + s orbitals defined on the two-dimensional (2D) Lieb lattice for the 2D version of DNL semimetals. The DNL states in these models are caused by the inversion of the bands with different symmetries and thus robust against spin–orbit interaction. By means of first-principles calculations, we demonstrate two candidate materials: Be2C and BeH2 monolayers, which have Fermi circles centred at Γ(0,0) and K(1/2,1/2) points, respectively. Their Fermi velocities are higher than that in graphene. The non-zero Z2 topological invariant accompanied by the edge states is revealed in these materials. This work opens an avenue for the design of 2D DNL semimetals.

Graphical abstract: Dirac node lines in two-dimensional Lieb lattices

Supplementary files

Article information

Article type
Paper
Submitted
18 Jan 2017
Accepted
24 May 2017
First published
25 May 2017

Nanoscale, 2017,9, 8740-8746

Dirac node lines in two-dimensional Lieb lattices

B. Yang, X. Zhang and M. Zhao, Nanoscale, 2017, 9, 8740 DOI: 10.1039/C7NR00411G

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