High-temperature quantum Hall effect in finite gapped HgTe quantum wells

TL;DR

This study demonstrates the quantum Hall effect in HgTe quantum wells at temperatures up to 60 K, revealing robust quantization linked to the material's band structure and confirming theoretical predictions about Landau levels and scaling behavior.

Contribution

It provides experimental evidence of high-temperature quantum Hall effect in finite-gap HgTe quantum wells and confirms the universality of scaling theory at elevated temperatures.

Findings

Quantum Hall effect observed up to 60 K in HgTe quantum wells.

Energy gaps between Landau Levels are around 25 meV, consistent with calculations.

Scaling coefficient κ aligns with universal scaling theory, unaffected by high temperatures.

Abstract

We report on the observation of the quantum Hall effect at high temperatures in HgTe quantum wells with a finite band gap and a thickness below and above the critical thickness $d_\textnormal{c}$ that separates a conventional semiconductor from a two-dimensional topological insulator. At high carrier concentrations we observe a quantized Hall conductivity up to 60\,K with energy gaps between Landau Levels of the order of 25\,meV, in good agreement with the Landau Level spectrum obtained from $\mathbf{k\cdot p}$-calculations. Using the scaling approach for the plateau-plateau transition at $\nu=2\rightarrow 1$, we find the scaling coefficient $\kappa =0.45 \pm 0.04$ to be consistent with the universality of scaling theory and we do not find signs of increased electron-phonon interaction to alter the scaling even at these elevated temperatures. Comparing the high temperature limit of the quantized Hall resistance in HgTe quantum wells with a finite band gap with room temperature experiment in graphene, we find the energy gaps at the break-down of the quantization to exceed the thermal energy by the same order of magnitude.