Thermoelectric effects in two-dimensional topological insulators

TL;DR

This paper investigates the thermoelectric properties of two-dimensional topological insulators, revealing how Berry curvature and different regimes influence thermoelectric coefficients and uncovering novel effects like the anomalous Nernst effect.

Contribution

It provides a comprehensive analysis of thermoelectric effects in 2D topological systems, including the application of Kelvin and Mott formulas across regimes and the behavior of edge modes near localization transitions.

Findings

Seebeck coefficient determined by Kelvin formula in Chern insulators

Berry curvature significantly affects thermoelectric coefficients

Anomalous Nernst effect arises from combined ballistic and dissipative regimes

Abstract

We explore the nontrivial thermoelectric properties of two-dimensional topological systems. For the Chern insulator, we show that the Seebeck coefficient is fully determined by the Kelvin formula, while the Nernst coefficient vanishes. For a two-dimensional electron gas with Rashba spin-orbit interactions we reveal how the Berry curvature affects the thermoelectric coefficients, and derive the Mott-like equation for thermopower. We predict a strong variation of the thermopower of a two-dimensional topological insulator with time-reversal symmetry in the ballistic and dissipative regimes. The Kelvin formula applies in the ballistic regime, while the Mott formula holds in the dissipative regime. Importantly, in a system with trapezoidal geometry, the combination of ballistic and dissipative regimes leads to the anomalous Nernst effect. Finally, we analyze a two-dimensional Anderson insulator, where edge modes show distinct temperature behavior of the Seebeck coefficient near the weak localization-strong localization transition temperatures. In the trivial phase, the thermopower exhibits a strong power law temperature dependence, while in the topological phase both power law and exponential dependences coexist.