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arXiv · 1608.01581

Strain Engineering of the Band Gap of HgTe Quantum Wells using Superlattice Virtual Substrates

Philipp Leubner·Lukas Lunczer·Christoph Brüne·Hartmut Buhmann·Laurens W. Molenkamp
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Abstract

The HgTe quantum well (QW) is a well-characterized two-dimensional topological insulator (2D-TI). Its band gap is relatively small (typically on the order of 10 meV), which restricts the observation of purely topological conductance to low temperatures. Here, we utilize the strain-dependence of the band structure of HgTe QWs to address this limitation. We use $\text{CdTe}-\text{Cd}_{0.5}\text{Zn}_{0.5}\text{Te}$ strained-layer superlattices on GaAs as virtual substrates with adjustable lattice constant to control the strain of the QW. We present magneto-transport measurements, which demonstrate a transition from a semi- metallic to a 2D-TI regime in wide QWs, when the strain is changed from tensile to compressive. Most notably, we demonstrate a much enhanced energy gap of 55 meV in heavily compressively strained QWs. This value exceeds the highest possible gap on common II-VI substrates by a factor of 2-3, and extends the regime where the topological conductance prevails to much higher temperatures.

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Philipp Leubner, Lukas Lunczer, Christoph Brüne, Hartmut Buhmann, Laurens W. Molenkamp. 2016-08-04. Strain Engineering of the Band Gap of HgTe Quantum Wells using Superlattice Virtual Substrates. https://doi.org/10.1103/physrevlett.117.086403

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