Today's computers rely on moving electrons to move data. Moving these charges, like the currents in electricity, can generate waste heat. What if an electron's spin, rather than its charge, could move data? In a special type of ultra-thin material, charge current and spin current only flow along the edges. Bending the film from flat to a half cylinder decoupled the charge current from the spin current. The up and down spins do not cancel each other out, resulting in a useful spin current. This creates a "pure" stream of spins that could move data with less energy.
Bending an exotic thin film is predicted to be a new tool to control and inject spin. Bending these special films could bring us closer to next-generation electronics that use spin to efficiently store and move data.
A future type of energy-efficient electronics is called spintronics. A challenge in spintronics is tuning how spins move to create current, called spin transport, in materials. Spin current and electrical current flow along the edge of 2-D topological insulators. Impressively, these exotic thin films (2-D materials) do not require strong magnetic fields to control the spin transport. Flat 2-D materials have shown no net spin current because of counter-propagating spin flowing along its edges. Bending the films, in a process called deformation, causes expansion or compression of a crystal lattice. Deformation is known to affect electronic properties. A research team led from the University of Utah performed calculations to investigate the effects of bending a flat 2-D topological insulator. They bent the film into a half cylinder. Researchers calculated the spin transport properties and spin texture in the material. The bending controlled the spin transport properties of the film. With bending, the spin current was tuned from zero to a maximum value. This work opens new avenues to tune and inject spin current by bending 2-D topological insulators.
University of Utah
Collaborative Innovation Center of Quantum Matter, Beijing
This work was primarily supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences. Additional support was provided by the National Natural Science Foundation of China and China Academy of Engineering Physics Laser. Computational resources were provided by National Energy Research Scientific Computing Center, a DOE Office of Science user facility; the University of Utah; and the Beijing Computational Science Research Center.
B. Huang, K.H. Jin, B. Cui, F. Zhai, J. Mei, and F. Liu, "Bending strain engineering in quantum spin Hall system for controlling spin currents." Nature Communications 8, 15850 (2017). [DOI: 10.1038/ncomms15850]