Topological Node-Line Semimetal in Compressed Black Phosphorus

TL;DR

This paper predicts that black phosphorus can become a three-dimensional topological node-line semimetal under pressure, featuring a protected band crossing near the Fermi level and associated surface states, with minimal impact from spin-orbit coupling.

Contribution

It introduces the possibility of black phosphorus hosting a topological node-line semimetal state under pressure, supported by first-principles and tight-binding analyses.

Findings

Existence of a topological node line near the Fermi energy

Presence of drumhead-like surface states on the (100) surface

Weak SOC opens a small gap but preserves surface states

Abstract

Based on first-principles calculations and tight-binding model analysis, we propose that black phosphorus (BP) can host a three-dimensional topological node-line semimetal state under pressure when spin-orbit coupling (SOC) is ignored. A closed topological node line exists in the first Brillouin zone (BZ) near the Fermi energy, which is protected by the coexistence of time-reversal and spatial inversion symmetry with band inversion driven by pressure. Drumhead-like surface states have been obtained on the beard (100) surface. Due to the weak intrinsic SOC of phosphorus atom, a band gap less than 10 meV is opened along the node line in the presence of SOC and the surface states are almost unaffected by SOC.