SPINTRONICS



Giant spin injection into semiconductor and THz pulse emission



Nat. Phys., 2019, doi: 10.1038/s41567-018-0406-3



Spintronics, which use the spin of electrons rather than their direct motion to carry information, has emerged as one of the leading alternatives to traditional electronics, promising faster information processing and lower energy consumption. Efficient spin injection into semiconductor is a crucial first step to realize useful spintronic devices, which remains an elusive challenge up to now. Recently, a joint group from Nanyang Technological University, the National University of Singapore, and the Agency for Science, Technology and Research (A*STAR) has achieved a breakthrough in the speed and efficiency of spin injection into semiconductor.



One member of the group has previously predicted the possibility of injecting massive ultrafast spin current across a ferromagnet/semiconductor interface. In this work, the joint group demonstrated the spin current injection experimentally. Ultrafast spin currents were generated by a laser pulse impinging on a Co film and injected into the adjacent monolayer MoS₂ — a two-dimensional semiconductor. Due to the high spin-orbit interaction of MoS ₂, the injected ultrafast spin currents were converted into transient charge currents, leading to the THz pulse emission which can be readily detected and analyzed. A giant spin current was measured, which was about four orders of magnitude larger than typical injected spin current densities in previous bulk semiconductor devices. This work represents a significant step in the development of ultrafast spintronics, which could be benefical for high-speed spintronic computers in the future.



Zheng Feng (Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu, China)



doi: 10.1088/1674-4926/40/7/070201