# Thermoelectric transport in two-dimensional topological insulator state based on HgTe quantum well

## TL;DR

This study investigates thermoelectric transport in HgTe quantum wells in the 2D topological insulator state, combining experimental measurements with a theoretical model to understand edge and bulk contributions.

## Contribution

The paper presents a comprehensive experimental and theoretical analysis of thermoelectric effects in 2D TIs, highlighting the dominance of bulk thermopower and the absence of anomalies near the band threshold.

## Key findings

- Ambipolar thermopower observed across charge neutrality point
- Thermopower increases linearly with temperature
- Bulk contribution dominates thermopower, edge affects resistance

## Abstract

The thermoelectric response of HgTe quantum wells in the state of two-dimensional topological insulator (2D TI) has been studied experimentally. Ambipolar thermopower, typical for an electron-hole system, has been observed across the charge neutrality point, where the carrier type changes from electrons to holes according to the resistance measurements. The hole-type thermopower is much stronger than the electron-type one. The thermopower linearly increases with temperature. We present a theoretical model which accounts for both the edge and bulk contributions to the electrical conductivity and thermoelectric effect in a 2D TI, including the effects of edge to bulk leakage. The model, contrary to previous theoretical studies, demonstrates that the 2D TI is not expected to show anomalies of thermopower near the band conductivity threshold, which is consistent with our experimental results. Based on the experimental data and theoretical analysis, we conclude that the observed thermopower is mostly of the bulk origin, while the resistance is determined by both the edge and bulk transport.