Temperature dependence of the quantized spin Hall conductance in high mobility HgTe quantum wells

The theoretically predicted helical edge states of a quantum spin Hall insulator were observed experimentally in the HgTe quantum wells (QWs), leading to the discovery of a new topological state of matter. Since then, the research has evolved dramatically with several theoretical and experimental investigations on HgTe QWs as well as other topological insulator materials. Here, we present temperature dependent measurements of the quantum spin Hall effect in HgTe QWs. The micro Hall bars of HgTe QWs have been fabricated using a refined wet etching process, which results in high carrier mobility for sample dimensions of the order of few microns. The spin Hall conductance is quantized to 2e²/h in the temperature range 30mK to 15 K. At T > 15 K, the conductance decreases following a power law dependence on temperature. Our results are significant for understanding the nature of backscattering mechanisms relevant in the quantum spin Hall regime in HgTe QWs.

We acknowledge financial support from the German Research Foundation (The Leibniz Program, DFG-Sonderforschungsbereich 1170 Tocotronics and Schwerpunktprogramm 1666), the Elitenetzwerk Bayern IDK Topologische Isolatoren.