标题： 可调控的约瑟夫森二极管效应，$0$-$π$转变和开关效应在超导体/二维外尔节线半金属/超导体结中 显示英文标题

标题： Controllable Josephson diode effect, $0$-$π$ transition and switch effect in the superconductor/two-dimensional Weyl nodal line semimetal/superconductor junctions

摘要： 我们使用格林函数方法研究超导体/二维外尔节线半金属/超导体结中的约瑟夫森效应。 当半导体中同时存在Rashba自旋-轨道耦合和外部磁场时，保护超电流对称性的对称性可能被破坏，从而实现具有超电流非对称性的约瑟夫森二极管效应。 通过实验可实现的磁场和Rashba自旋-轨道耦合值，可以实现超过$40\%$的高效率。 二极管效率可以通过磁场的方向和大小以及自旋-轨道耦合的强度轻松控制。 当没有自旋-轨道耦合或没有外部场时，约瑟夫森二极管效应消失，但电流-相位差关系仍然表现出对场或耦合的强依赖性。 如果旋转场的方向或改变场的大小和耦合的强度，可以在结中形成可调的$0$-$\pi$转变和超电流的开关效应。 获得的约瑟夫森二极管效应、$0$-$\pi$转变和超电流的开关效应有助于基于节线半金属的量子器件的设计。 显示英文摘要

摘要： We study the Josephson effects in the superconductor/two-dimensional Weyl nodal line semimetal/superconductor junctions using the Green's function method. When the Rashba spin-orbit coupling and an external magnetic field coexist in the semimetal, the symmetries protecting the reciprocity of supercurrent can be broken and the Josephson diode effect with the nonreciprocity of supercurrent can be realized. A high efficiency exceeding $40\%$ can be achieved with the experimentally accessible values of the magnetic field and the Rashba spin-orbit coupling. The diode efficiency can be easily controlled by the direction and magnitude of the field and the strength of the spin-orbit coupling. When the spin-orbit coupling is absent or the external field is absent, the Josephson diode effect vanishes but the current-phase difference relations still show strong dependence on the field or the coupling. The tunable $0$-$\pi$ transition and the switch effect of supercurrent in the junctions can be formed if the direction of the field is rotated or the magnitude of the field and the strength of the coupling are changed. The obtained Josephson diode effect, the $0$-$\pi$ transition and the switch effect of supercurrent are helpful in the design of the quantum devices based on nodal line semimetals.