Tuning topologically nontrivial states in the BHT-Ni metal organic framework

TL;DR

This study uses first principles calculations to demonstrate how electron doping can induce quantum spin Hall and quantum anomalous Hall states in the BHT-Ni metal organic framework, revealing tunable topological properties.

Contribution

It shows how electron doping levels can switch the topological states in BHT-Ni, including the effects of symmetry breaking on these states.

Findings

Quantum spin Hall state at low doping with nontrivial band gap

Quantum anomalous Hall state at high doping with quantized Hall conductivity

Symmetry breaking influences the presence of valley and spin Hall effects

Abstract

Using first principles calculations, we have demonstrated the creation of multiple quantum states, in the experimentally accessible metal organic framework BHT-Ni. Specifically, quantum spin Hall and quantum anomalous Hall states are induced by two and four electron doping, respectively. The geometrical symmetry breaking, is also investigated. For a low electron doping concentration of two electrons per unit cell, the Fermi energy shifts to a nontrivial band gap, between Dirac bands and a quantized spin Hall conductivity is predicted. Subsequently in a high electron doping concentration, Anomalous Hall conductivity with a quantized value was observed. In addition, for centrosymmetric (trans-like) and non-centrosymmetric (cis-like) structures, we found that the trans-like structure preserves quantum spin Hall and quantized spin Hall conductivity. In contrast, in the cis-like structure, space inversion symmetry breaking leads to the appearance of valley Hall effect and the disappearance of spin Hall conductivity.