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arXiv 1608.01581cond-mat.mtrl-sci
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基于超晶格虚拟衬底的HgTe量子阱带隙应变工程

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

摘要:

碲化汞量子阱是一种二维拓扑绝缘体。它的带隙相对较小(通常在10 meV的量级),这限制了对低温下纯拓扑电导的观察。在这里,我们利用应变依赖性的能带结构的碲化汞量子阱来解决这个限制。我们使用GaAs上的$\text{CdTe}-\text{Cd}_{0.5}\text{Zn}_{0.5}\text{Te}$应变层超晶格作为虚拟衬底,通过可调的晶格常数来控制量子阱的应变。我们提出的磁输运测量,这表明从半金属过渡到二维TI制度在宽量子阱,当应变从拉伸到压缩。最值得注意的是,我们证明了一个大大增强的能隙的55毫电子伏在严重压缩应变量子阱。这个值超过了常见的II-VI衬底上的最高可能的间隙的2-3倍,并扩展了拓扑电导占主导地位的制度,以更高的温度。

英文摘要:

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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