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Transport properties of superconducting hybrid structures based on quantum wells with normal and inverted band ordering

基于正向和反向能带有序量子阱的超导混合结构的输运特性

基本信息

批准号：
317332961
负责人：
Dr. Alena Astakhova
金额：
--
依托单位：
Institut für Mathematische Physik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/317332961?language=en
关键词：
Transport properties superconducting hybrid structures

项目摘要

In our project, we will study theoretically the transport properties of hybrid structures based on HgTe and InAs/GaSb quantum wells (QWs) in the insulating or semiconducting state with the normal and inverted band ordering. QWs proximity-coupled to an s-wave superconductor will be considered, whereby special attention will be given to the influence of the Rashba and Dresselhaus spin-orbit interactions on the transport properties. Further, the transport properties of the QW coupled to a normal and a superconducting contact in the presence of the Zeeman field will be analyzed. Interesting properties of the hybrid structures predicted recently in the band structure calculations, which are caused by the spin-orbit interaction, will be studied here analyzing transport. The first one is a reversion of the chirality of Majorana edge states in a topological superconductor induced in a QW by changing the relative strength of the Rashba and Dresselhaus spin-orbit terms, an effect that goes along with a change of the bulk topological invariant. The second feature is the high tunability of the Rashba spin-orbit energies and the effective g-factors with a moderate variation of potential drop across the QW width. These features could have a significant effect on the transport properties of the hybrid structures and offer additional methods of transport tuning.Moreover, we will study transport properties of a QW in the inverted regime with a magnetically gapped region connected to the superconducting contacts. Two cases will be considered: when magnetic and superconducting regions are induced at one edge of the QW, and when they extend over the whole width of the structure, i.e. over the helical edge states at the opposite boundaries of the QW. In the second case four Majorana fermions (predicted earlier to appear at the interface between superconducting and magnetically gapped regions in the QW) build a processable fermionic qubit with logical basis states of the same parity. We expect, that the qubit can be tuned externally changing the phase difference between the Josephson junctions as well as an overlap of the helical edge states at the two boundaries by gate voltage, which might be interesting for quantum computation processing with non-abelian anyons.We will analyze the influence of disorder on the transport properties of hybrid structures. In the case of the inverted regime of the QW both bulk and edge state contributions to the transport in the structures will be considered simultaneously. This will provide more realistic estimations of the transport properties in the analyzed systems and will be important for the interpretation of future experiments.

在本项目中，我们将从理论上研究HgTe和InAs/GaSb量子威尔斯（QW）混合结构在绝缘态和半导体态下的输运性质。量子阱邻近耦合的s波超导体将被考虑，其中特别注意的是将给予Rashba和Dresselhaus自旋轨道相互作用的输运性质的影响。此外，量子阱耦合到正常和超导接触在塞曼场的存在下的输运性质进行了分析。有趣的性质的混合结构预测最近在能带结构的计算，这是由自旋-轨道相互作用，将在这里研究分析运输。第一种是通过改变Rashba和Dresselhaus自旋轨道项的相对强度，在量子阱中诱导拓扑超导体中Majorana边缘态的手征的反转，这种效应沿着体拓扑不变量的变化。第二个特征是Rashba自旋轨道能量和有效g因子的高可调性，并且在量子阱宽度上具有适度的势降变化。这些特性可能对混合结构的输运性质产生重要影响，并提供额外的输运调谐方法。此外，我们还将研究与超导接触相连的磁隙区的量子阱在反转态的输运性质。将考虑两种情况：当在QW的一个边缘处感应出磁性和超导区域时，以及当它们在结构的整个宽度上延伸时，即在QW的相对边界处的螺旋边缘状态上延伸时。在第二种情况下，四个马约拉纳费米子（早先预测出现在量子阱中超导和磁隙区域之间的界面）建立了一个可处理的费米子量子位，具有相同奇偶性的逻辑基态。我们期望，量子比特可以外部调谐，改变约瑟夫森结之间的相位差，以及在两个边界处的螺旋边缘状态的重叠通过栅极电压，这可能是有趣的量子计算处理与非阿贝尔anyons.我们将分析无序对混合结构的输运性质的影响。在量子阱的反转制度的情况下，体和边缘状态的结构中的传输的贡献将被同时考虑。这将提供更现实的估计的传输特性在分析系统，并将是重要的解释未来的实验。