Ultra Low Temperature Conductance of Helical Edge States in InAs/GaSb 2D Topological Insulator*

Inverted InAs/GaSb quantum wells have been shown to be a 2D topological insulator hosting helical edge states. For mesoscopic samples, quantized conductance plateaus of 2e$^{2}$/h have been observed. On the other hand, the longitudinal resistance in long samples increased linearly with device length, indicating certain scattering processes occurred in the helical edge. Moreover, edge states of InAs/GaSb system have a small Fermi velocity \textit{V\textunderscore F}, suggesting that interaction effects may play an important role in their electronic transport properties. We report work in progress for conductance measurements of InAs/GaSb helical edge states in ultra low temperatures. Experiments are performed in two millikelvin dilution refrigerators instrumented for fractional quantum Hall effect studies, one of them having attained 6mK electron temperature.