Topological phases in hydrogenated gallenene and in its group elements

TL;DR

This paper uses DFT calculations to identify 2D nodal line semimetal phases in hydrogenated gallenene and group 13 elements, revealing their topological properties and potential for spintronics.

Contribution

It demonstrates the existence of 2D NLSM phases in hydrogen passivated group 13 elements without SOC and shows how strain and SOC induce topological phase transitions.

Findings

2D NLSM phase hosted on hydrogenated gallenene surface

Gallenane becomes a quantum spin Hall insulator under strain and SOC

Potential for room temperature spintronics applications

Abstract

Nontrivial topology of Dirac (DSMs), Weyl (WSMs) and nodal line semimetals (NLSMs) are delineated by the novel band crossings near the Fermi level in the bulk and the appearance of exotic surface states. Among them, nodal line semimetals have gained immense interest due to the formation of one-dimensional nodal ring near the Fermi level. Using density funtional theory (DFT) calculations, we report that two dimensional (2D) NLSM phase can be hosted on hydrogen passivated (010) surface of gallium (gallenene) and on other group 13 elements, without inclusion of spin-orbit coupling (SOC). NLSM in these 2D systems is protected by the presence of crystalline (CS) along with inversion (IS) and the time reversal symmetry (TRS). In the presence of SOC, aluminane preserved its topological NLSM phase while in other single layered group 13 elements, a gap opened at the nodal point due to relatively stronger SOC effect. On applying tensile strain along with the inclusion of SOC, hydrogen passivated gallenene (gallenane) evolves into quantum spin Hall insulator with an indirect bandgap of 28 meV. The appearance of long range dissipationless linearly dispersive helical edge states and a large gap in gallenane make it promising for room temperature spintronics applications.