# Radiative Decay of Bound Electron Pairs in Two-Dimensional Topological Insulators

## TL;DR

This paper investigates the radiative decay of bound electron pairs in 2D topological insulators, revealing that their stability varies with topological phase and band dispersion, with potential decay times around 1 nanosecond.

## Contribution

It provides a theoretical analysis of the decay times of bound electron pairs in 2D topological insulators, highlighting the influence of topological properties and band dispersion on their stability.

## Key findings

- Decay time is much longer in the topological phase.
- Decay time depends on band dispersion and topological properties.
- Estimated decay time is approximately 1 nanosecond in HgTe/CdHgTe heterostructures.

## Abstract

Bound electron pairs (BEPs) with energy in the band gap are interesting because they can participate in charge and spin transport in modern topologically nontrivial materials. We address the problem of their stability and study the radiative decay of the BEPs formed due to the negative reduced effective mass in two-dimensional topological insulators. The decay time is found to be rather large on the scale of the characteristic relaxation times of the electron system and significantly dependent on the topological properties and dispersion of the band states. In topological phase the decay time is much longer than in the trivial one, and is estimated as $\sim$1~ns for the HgTe/CdHgTe heterostructures. However, the longest decay time is in the topological phase with nearly flat dispersion in the band extema.