Controllable chiral Majorana modes by noncollinear magnetic configuration in a topological Josephson junction

Recently, theory and experiment both have confirmed a Majorana zero mode to induce selective equal spin Andreev reflection (SESAR). Herein, we theoretically present controllable chiral Majorana modes (CMMs) by noncollinear magnetic configuration in a Josephson junction on a topological insulator with two ferromagnetic insulators (FIs) sandwiched in between two superconductors (SCs). It is shown that an additional phase shift is induced by the different chirality of the CMMs at the two FI/SC interfaces, whose magnitude is determined by misorientational angle θ, which can be administrated by the Andreev bound surface energies. The angle θ is found to result in the 0-π state transition and Φ0 supercurrent. Particularly, due to the SESAR, the coexistence of fully spin-polarized spin-singlet and -triplet correlations is exhibited with the exclusive fully spin-polarized spin-triplet (singlet) correlation corresponding to the ferromagnetic (F) [antiferromagnetic (AF)] configuration. For the two magnetizations only along y-axis, there exist no additional phase shift and topological supercurrent with fully spin-polarized correlations, especially, the supercurrent in the AF configuration is a lot larger than that in the F one, which is strongly dependent on the exchange field strength and FI length, thus even leading to 100% supercurrent magnetoresistance. The results can be employed to not only identify the topological SCs but also design a perfect topological supercurrent spin valve device.

Peculiarities of magnetic moment switching in the φ(0) junction

We have investigated the dynamics of magnetization under a current pulse in a φ0 - junction with a direct coupling between the magnetic moment and the superconducting current. The correspondence between the magnetization value at the end of the pulse mz * and the realization of the magnetization reversal along the easy axis of the ferromagnetic is considered. The crucial influence of the ratio w of the ferromagnetic frequency to the characteristic frequency of the Josephson junction on the results of reversal predictions is demonstrated. Effect of w magnitude on the manifestation of periodicity bands in the mz * dependence on the model parameters is shown. There is a critical value of the Gilbert damping, above which the magnetization reversal is not realized. It is shown that at small w the magnitude mz * can be as a criterion of magnetization reversal. I.e., if mz * <0, the magnetization reversal would happen with 100 percent probability. The results can be used in various areas of superconducting spintronics, in particular, to create a memory element based on the Josephson $ {\varphi_0} $ junction

Switchable Spiral Josephson junction: A superconducting spin-valve proposal

We propose a superconducting spin valve based on a Josephson junction with B20-family magnetic metal as barrier material. Our analysis shows that the states of this element can be switched by reorienting the intrinsic non-collinear magnetization of the spiral magnet. This reorientation modifies long-range spin-triplet correlations and thereby influences strongly the critical Josephson current. Compared to superconducting spin valves proposed earlier, our device has the following advantages: (i) it contains only one barrier layer, which makes it easier to fabricate and control; (ii) its ground state is stable, which prevents uncontrolled switching; (iii) it is compatible with devices of low-T Josephson electronics. This device may switch between two logical states which exhibit two different values of critical current, or its positive and negative value. I.e. 0-π switch is achievable on one simple Josephson junction.