基于单层二硫化钼的谷超导电子学研究

Recently, from theoretical and experimental point of view, great interest has been aroused in research on the excellent electrical and optical properties of monolayer molybdenum disulfide due to its exciting developments in experiments. In the project, the physical phenomena of Andreev reflection(Retro- and Specular-), crossed Andreev reflection(Retro- and Specular-), and Andreev bound state under the influence of spin-valley coupling and spin-orbit coupling through monolayer molybdenum disulfide based superconducting heterojunctions are considered. Subsequently the physical essences of those intriguing phenomena will be revealed. Meanwhile, the transport properties of those structures will be investigated which provide a crucial reference to realize valley superconducting quantum devices based on monolayer molybdenum disulfide. Quantum devices with superconductors lead to many peculiar properties, such as higher sensitivity, lower energy cost, fast response speed, etc, which bring us a wider prospective application in valleyelectronics based on monolayer molybdenum disulfide. Spin-valley coupling due to inversion symmetry breaking and strong spin-orbit coupling which only live in monolayer molybdenum disulfide and other group-VI transitionmetal dichalcogenides should therefore yield a series of intriguing valley resolved quantum phenomena not known from earlier studies. Therefore, this project not only has potential application value, also possesses significant theoretical research significance.

随着最近几年单层二硫化钼实验方面的令人振奋的发展，对单层二硫化钼相关电学和光学性质的研究已成为目前理论和实验研究领域的一个研究热点。本项目旨在揭示自旋轨道耦合效应、自旋-谷耦合和单层二硫化钼基超导异质结内 Andreev 反射（Retro- 和 Specular-）、Crossed Andreev 反射（Retro- 和 Specular-）以及 Andreev 束缚态之间的相互作用关系及其物理本质。与此同时澄清相关超导异质结的量子输运特性及其调制规律，为单层二硫化钼基谷超导量子器件的设计提供理论指导。由于超导量子器件具有灵敏度高、能耗低和响应速度快等一系列特点，使得该类器件具有广阔的应用前景。此外，我们可以预期对单层二硫化钼类材料所特有的自旋-谷耦合的研究将得到一系列全新的谷相关量子现象。因此本项目的研究不但具有潜在的应用价值，而且具有重要的理论研究意义。

在本项目中，我们基于 Dirac–Bogoliubov–de Gennes 方程对二硫化钼（过渡金属硫化物）基超导异质结内费米子的量子输运特性进行了相关的仔细研究。我们首先仔细探讨了 Andreev 反射对自旋轨道耦合的响应性能，然后分析该量子器件隧穿电导对入射准粒子能量、结构参数以及自旋轨道耦合效应的调制规律。结果显示 Andreev 反射和 Crossed Andreev 反射对自旋轨道耦合具有敏感的依赖关系，我们可以基于自旋轨道耦合对该量子器件的输运特性进行具体的调制。由于自旋轨道耦合可以由一个外加电极直接控制，所以利用该方法我们就可以得到一个全电学的量子器件。由于自旋-能谷耦合效应，基于 Crossed Andreev 反射，我们还可以获取100%的纯谷量子纠缠态用于量子计算。此外，我们对二硫化钼（过渡金属硫化物）基约瑟夫森结内超流对自旋轨道耦合的依赖关系进行了仔细的研究。研究结果显示结内 Andreev 束缚态对自旋轨道耦合和结构参数存在着紧密的依赖关系。我们可以通过自旋轨道耦合效应、外加门电压以及具体结构对结内的 Andreev 束缚态进行具体的调制，进而对约瑟夫森结内临界超流、偏斜度和流相关系进行相应的调控。我们的研究显示自旋轨道耦合不仅可以作为调制 Andreev 反射和 Crossed Andreev 反射一个新的途径方法，而且由其调控的超导异质结构可以为新型二硫化钼（过渡金属硫化物）基纳米谷电子学器件的设计提供一个新选择。