We report transport measurements of strained InAs/In${}_x$Ga${}_{1-x}$Sb composite quantum wells (CQWs) in the quantum spin Hall phase, focusing on the control of the energy gap through structural parameters and an external electric field. For highly strained CQWs with $x=0.4$, we obtain a gap of 35 meV, an order of magnitude larger than that reported for binary InAs/GaSb CQWs. Using a dual-gate configuration, we demonstrate an electrical-field-driven topological phase transition, which manifests itself as a re-entrant behavior of the energy gap. The sizeable energy gap and high bulk resistivity obtained in both the topological and normal phases of a single device open the possibility of electrical switching of the edge transport.

中文翻译：

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InAs / InxGa1-xSb复合量子阱中的能隙调整和门控拓扑相变

我们报告了应变InAs / In的传输测量${}_X$嘎${}_{\mathrm{1个}-X}$量子自旋霍尔相中的Sb复合量子阱（CQW），重点在于通过结构参数和外部电场控制能隙。对于高度紧张的CQW$X=0.4$，我们得到的间隙为35 meV，比报道的二元InAs / GaSb CQW的间隙大一个数量级。使用双栅极配置，我们演示了电场驱动的拓扑相变，将其表现为能隙的可重入行为。在单个器件的拓扑和正态阶段都获得了相当大的能隙和较高的体电阻率，这为边缘传输的电切换提供了可能。