Interfacial Spin Orbit Research Articles

Conversion of spin and charge currents in magnetic and non-magnetic systems

We formulate the law of conversion between spin current and charge current in several classes of materials including ferromagnetic, paramagnetic and spin-orbit coupled systems. We find that the interpretation of spin current is highly non-trivial, and we have identified pure and composite spin currents. For an interfacial Rashba spin-orbit coupled Hamiltonian, we show that the spin transport is much closer to that in ferromagnets than in non-magnetic materials. In particular, we show that an in-plane charge current in layered structures will generate a pure spin current flowing perpendicular to the Rashba spin-orbit coupled interface, and vice versa. Application of the spin-charge current conversion in several experimental realizations is discussed.

Chirality from Interfacial Spin-Orbit Coupling Effects in Magnetic Bilayers

As nanomagnetic devices scale to smaller sizes, spin-orbit coupling due to the broken structural inversion symmetry at interfaces becomes increasingly important. Here, we study interfacial spin-orbit coupling effects in magnetic bilayers using a simple Rashba model. The spin-orbit coupling introduces chirality into the behavior of the electrons and through them into the energetics of the magnetization. In the derived form of the magnetization dynamics, all of the contributions that are linear in the spin-orbit coupling follow from this chirality, considerably simplifying the analysis. For these systems, an important consequence is a correlation between the Dzyaloshinskii-Moriya interaction and the spin-orbit torque. We use this correlation to analyze recent experiments.

Odd-frequency spin-triplet pairing states in half-metal/d-wave superconductor junctions

Based on the extended Blonder–Tinkham–Klapwijk formalism, differential conductance spectrum of d-wave superconductor/half-metal junctions is investigated as a function of the interfacial spin–orbit coupling (SOC). It shows that the SOC modifies the interfacial spin-flip scattering, enabling spin-singlet and spin-triplet pairing conversion with the aid of equal-spin-band Andreev reflection. A zero-bias conductance peak has been found, which is closely related to the zero energy Andreev bound state of equal-spin pairing correlation induced by the broken electron-hole symmetry of model Hamiltonian and gives strong evidences for the odd-frequency spin-triplet pairing states.

Spin Current in Generic Hybrid Structures due to Interfacial Spin-Orbit Scattering

We demonstrate a general principle that hybrid structures of any sort inevitably will give rise to a pure spin current flowing parallel to the interface region when a charge current is injected. This stems from the broken mirror symmetry near the interface which gives rise to spin-orbit coupling that deflects incoming electrons in a spin-discriminating fashion. We establish a general analytical condition for the appearance of this effect, and calculate the transverse spin current explicitly using two different models. In addition, we investigate how the process of Andreev reflection influences this phenomenon in the scenario where one of the materials is superconducting.