title: Strain Engineering of the Band Gap of HgTe Quantum Wells Using Superlattice Virtual Substrates.
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 CdTe-Cd_{0.5}Zn_{0.5}Te strained-layer superlattices on GaAs as virtual substrates with adjustable lattice constant to control the strain of the QW. We present magnetotransport measurements, which demonstrate a transition from a semimetallic 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.
authors: Experimentelle Physik III, Physikalisches Institut, Universitüt Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors: Philipp
authors: P
authors: Leubner
authors: Experimentelle Physik III, Physikalisches Institut, Universitüt Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors: Lukas
authors: L
authors: Lunczer
authors: Experimentelle Physik III, Physikalisches Institut, Universitüt Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors: Christoph
authors: C
authors: Brüne
authors: Experimentelle Physik III, Physikalisches Institut, Universitüt Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors: Hartmut
authors: H
authors: Buhmann
authors: Experimentelle Physik III, Physikalisches Institut, Universitüt Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors: Laurens W
authors: LW
authors: Molenkamp