Thermal dissipation of the quantum spin Hall edge states in HgTe/CdTe quantum well

TL;DR

This study investigates how different dissipation sources affect thermal dissipation in quantum spin Hall edge states, revealing conditions under which they remain dissipationless or become dissipative, with implications for reducing heat loss.

Contribution

It provides a detailed analysis of the impact of normal and spin dissipation sources on thermal dissipation in quantum spin Hall edge states, including effects of disorder.

Findings

Helical edge states are dissipationless under normal dissipation sources.

Spin dissipation sources induce thermal dissipation and voltage drops.

Disorder influences the thermal dissipation behavior.

Abstract

Quantum spin Hall effect is characterized by topologically protected helical edge states. Here we study the thermal dissipation of helical edge states by considering two types of dissipation sources. The results show that the helical edge states are dissipationless for normal dissipation sources with or without Rashba spin-orbit coupling in the system, but they are dissipative for spin dissipation sources. Further studies on the energy distribution show that electrons with spin-up and spin-down are both in their own equilibrium without dissipation sources. Spin dissipation sources can couple the two subsystems together to induce voltage drop and nonequilibrium distribution, leading to thermal dissipation, while normal dissipation sources cannot. With the increase of thermal dissipation, the subsystems of electrons with spin-up and spin-down evolve from non-equilibrium finally to mutual equilibrium. In addition, the effects of disorder on thermal dissipation are also discussed. Our work provides clues to reduce thermal dissipation in the quantum spin Hall systems