# From a normal insulator to a topological insulator in plumbene

## TL;DR

This study reveals that doped plumbene can transition from a normal insulator to a robust topological insulator with a large gap, suitable for room-temperature quantum spin Hall applications.

## Contribution

The paper demonstrates that electron doping and external fields can induce topological phases in plumbene, providing a theoretical basis for spin-valley filtering devices.

## Key findings

- Doped plumbene becomes a topological insulator with a large bulk gap.
- External strain does not destroy the topological state.
- Phase diagrams show tunable electronic states under external fields.

## Abstract

Plumbene, similar to silicene, has a buckled honeycomb structure with a large band gap ($\sim 400$ meV). All previous studies have shown that it is a normal insulator. Here, we perform first-principles calculations and employ a sixteen-band tight-binding model with nearest-neighbor and next-nearest-neighbor hopping terms to investigate electronic structures and topological properties of the plumbene monolayer. We find that it can become a topological insulator with a large bulk gap ($\sim 200$ meV) through electron doping, and the nontrivial state is very robust with respect to external strain. Plumbene can be an ideal candidate for realizing the quantum spin Hall effect at room temperature. By investigating effects of external electric and magnetic fields on electronic structures and transport properties of plumbene, we present two rich phase diagrams with and without electron doping, and propose a theoretical design for a four-state spin-valley filter.