Long-distance spin communication via ambipolar conductor with electron-hole spin exchange interaction

Spin accumulation in a nonmagnetic (N) metal embedded between two ferromagnetic metals is still crucial in current spintronics because long-distance spin communication via the N metal can make all-spin logic (ASL) devices feasible. Graphene is almost the only N-region material suitable for ASL devices because its low intrinsic spin-orbit coupling results in a spin diffusion length, lN , of over 30 mu m at room temperature, but long-distance spin communication beyond lN remains difficult. The present study proposes a way to remove the restriction caused by lN . In our proposal, an ambipolar conductor, in which electron and hole contribute to electronic conduction and interact with each other, is used for the N-region in a double-heterojunction magnetic structure. When the electron-hole interaction is accompanied by spin exchange, long-distance spin communication characteristic is predicted. Approximately 70 types of ambipolar conductors, including elemental metals and metal alloys, are available. Hence, this material variation may open a new spintronics field, ambipolar spintronics, which may realize operation mechanisms that cannot be achieved using conventional single-band metals. Finally, we present a comprehensive argument on the interface-mediated coupling mechanism between spins and charges, which is the basis of the generation of the spin-coupled interface voltage.