Recently, Professor Lingling Tao's research group from the School of Physics made significant progress in spintronics. Their findings, titled Ferroelectric Spin-Orbit Valve Effect, were published in Physical Review Letters. This work proposes a novel semiconductor spintronic device, which provides an important alternative for designing the next-generation high-speed and low-energy nonvolatile memory.
Nowadays, the all-electric semiconductor spintronic devices are rare and the previously proposed spin-field-effect transistor has not yet been confirmed. In this context, Tao’s group proposes a pioneering all-electric nonvolatile spin-orbit valve device. In ferroelectric semiconductors, the polarity of the spin-orbit coupling is locked to its polarization, which enables a nonvolatile control of the spin-orbit coupling. Based on this, Tao et al. proposed the ferroelectric spin-orbit valve device, where two ferroelectric semiconductors are separated by a thin barrier layer. When polarization is parallel, charge carriers can be efficiently transmitted through the device leading to a high conductance state (ON state). On the contrary, when polarization is antiparallel, electrons incoming from one FE electrode are reflected by the other electrode due to the absence of available states with that spin state at a given transverse momentum. Thus, a low conductance (OFF state) is expected. Based a tight-binding model and density functional theory calculations, a giant spin-orbit valve effect that is characterized by the conductance change of several orders in magnitude was demonstrated. This work enriches spin-orbit physics of ferroelectrics and proposes a new type of all-electric control of a nonvolatile spin-orbitronic device, which holds promise for future electronic and memory applications.
Paper link: https://doi.org/10.1103/PhysRevLett.134.076801
Schematic working principle for the ferroelectric spin-orbit valve
