&Bullet; physics 14, p91
Researchers demonstrate that they can control the direction of polarization of a spin current without having to apply a magnetic field, which could help implement energy-efficient spintronic devices.
Spin currents can live much longer in graphene than in other materials, making the material an ideal platform for future spintronic devices. But there is a problem: In order to manipulate the spin currents of graphene, researchers have to apply a magnetic field to the material. The necessary hardware is difficult to integrate into circuits, which limits the size reduction of small graph-based spin components. Josep Ingla-Aynés from the Nanoscience Cooperative Research Center (CIC NanoGUNE), Spain, and colleagues have now demonstrated a method to manipulate graphene spin currents – at room temperature – only with electric fields  .
The team punched a sheet of tungsten diselenide on a sheet of two-layer graphene and heated the two materials to bond them together. Then they patterned the structure with a series of electrodes, which they used to apply an in-plane electric field and gate voltage, and inject a spin current into the graphene. The experiments were carried out at 50 K and at room temperature.
At both temperatures, the team observed that they could change the direction of polarization of the spin current by changing the magnitude of both the in-plane electric field and the gate voltage. They say that control comes from the spin-orbit coupling in the tungsten-diselenide layer. This effect creates an effective magnetic field in the graph that is sufficient to change the spin angle.
Ingla-Aynés says the demonstration is a room temperature version of the long-sought spin transistor “Datta Das”. The spin transistor from Datta Das is a component whose electrical resistance can be switched from high to low by changing the direction of polarization of the spin current. Such devices have been implemented at low temperatures using two-dimensional electron gases, but not at higher temperatures.
Katherine Wright is assistant editor of physics.
- J. Ingla-Aynés et al., “Electrical control of the spin precession induced by Tal-Zeeman spin-orbit coupling at room temperature”, Physical review letters127, 047202 (2021).