论文标题
开关效果和$ 0 $ - $ - $π$过渡在Ising超导体Josephson连接
Switch effect and $0$-$π$ transition in Ising superconductor Josephson junctions
论文作者
论文摘要
从理论上讲，我们研究了约瑟夫森电流，用于iSing超导体半导体 - 金属上升超导体连接。通过求解Bogoliubov-De Gennes方程，获得了由离散的Andreev水平和连续频谱贡献的Josephson电流。对于非常短的连接，由于库珀对的直接隧道占据了约瑟夫森电流，因此电流差异关系与磁化方向无关，这与常规的超导体 - ferromagnet-supductuctuctor nctions相同。另一方面，当半金属的长度与超导相干长度相似或大时，旋转三个旋转的约瑟夫森效应就会发生并主导约瑟夫森电流。在这种情况下，电流差异关系显示出与周期π的强磁敏感行为。当磁化方向指向$ \ pm $ z方向时，无论相位差如何，电流都是零。但是，当磁化方向平行于接线平面时，电流具有较大的值，这导致了约瑟夫森电流的完美开关效果。此外，我们发现较长的连接可以容纳0个状态和πState，并且可以通过改变磁化方向来实现$ 0 $ - $π$的过渡。开关效果的物理起源和$ 0 $ - $π$的转变是从自旋三角体Andreev反射的角度来解释的，Ising配对订单参数和Ginzburg-Landau类型的自由能。此外，还研究了化学电位的影响，磁化幅度和ISIN旋转轨道耦合对开关效果的强度以及$ 0 $ - $π$的转换。此外，还研究了二维的约瑟夫森连接，我们表明旋转三个约瑟夫森效应总是可以存在的。
We theoretically study the Josephson current in Ising superconductor-half-metal-Ising superconductor junctions. By solving the Bogoliubov-de Gennes equations, the Josephson currents contributed by the discrete Andreev levels and the continuous spectrum are obtained. For very short junctions, because the direct tunneling of the Cooper pair dominates the Josephson current, the current-phase difference relation is independent of the magnetization direction, which is the same as the conventional superconductor-ferromagnet-superconductor junctions. On the other hand, when the length of the half-metal is similar to or greater than the superconducting coherence length, the spin-triplet Josephson effect occurs and dominates the Josephson current. In this case, the current-phase difference relations show the strong magnetoanisotropic behaviors with the period π. When the magnetization direction points to the $\pm$ z directions, the current is zero regardless of the phase difference. However, the current has a large value when the magnetization direction is parallel to the junction plane, which leads to a perfect switch effect of the Josephson current. Furthermore, we find that the long junctions can host both the 0 state and πstate, and the $0$-$π$ transitions can be achieved with the change of the magnetization direction. The physical origins of the switch effect and $0$-$π$ transitions are interpreted from the perspectives of the spin-triplet Andreev reflection, the Ising pairing order parameter and the Ginzburg-Landau type of free energy. In addition, the influences of the chemical potential, the magnetization magnitude, and the strength of the Ising spin-orbit coupling on the switch effect and $0$-$π$ transitions are also investigated. Furthermore, the two-dimensional Josephson junctions are also investigated and we show that the spin-triplet Josephson effect can exist always.
