Large spin Hall conductivity and excellent hydrogen evolution reaction activity in unconventional PtTe1.75 monolayer

Two-dimensional (2D) materials have gained lots of attention due to the potential applications. In this work, we propose that based on first-principles calculations, the (2x2) patterned PtTe2 monolayer with kagome lattice formed by the well-ordered Te vacancy (PtTe1.75) hosts large and tunable spin Hall conductivity (SHC) and excellent hydrogen evolution reaction (HER) activity. The unconventional nature relies on the A1@1b band representation (BR) of the highest valence band without SOC. The large SHC comes from the Rashba spin-orbit coupling (SOC) in the noncentrosymmetric structure induced by the Te vacancy. Even though it has a metallic SOC band structure, the Z(2) invariant is well defined due to the existence of the direct band gap and is computed to be nontrivial. The calculated SHC is as large as 1.25x10(3h/e) (omega)(-1) at the Fermi level (E-F). By tuning the chemical potential from E-F - 0.3 to E-F + 0.3 eV, it varies rapidly and monotonically from -1.2 x 10(3) to 3.1x10(3h/e) (omega)(-1). In addition, we also find the Te vacancy in the patterned monolayer can induce excellent HER activity. Our results not only offer a new idea to search 2D materials with large SHC, i.e., by introducing inversion-symmetry breaking vacancies in large SOC systems, but also provide a feasible system with tunable SHC (by applying gate voltage) and excellent HER activity.

Automated summary

In this study, a (2x2) patterned PtTe2 monolayer with a kagome lattice structure formed by Te vacancies was investigated. The monolayer was found to exhibit large and tunable spin Hall conductivity (SHC) and excellent hydrogen evolution reaction (HER) activity. The large SHC was attributed to the Rashba spin-orbit coupling induced by the Te vacancies, and the nontrivial Z(2) invariant was determined by the presence of a direct band gap. The calculated SHC ranged from 1.25x10(3h/e) (omega)(-1) to -1.2 x 10(3) to 3.1x10(3h/e) (omega)(-1) by adjusting the chemical potential. Additionally, the monolayer also showed promising HER activity. This work not only provides a new strategy to search for 2D materials with large SHC, but also demonstrates a feasible system with tunable SHC and excellent HER activity.