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Large Spin-Orbit Coupling Semiconductors and Their Spintronics Applications
Date: 2016/5/20             Browse: 280

Large Spin-Orbit Coupling Semiconductors and Their Spintronics Applications

Speaker: Xufeng Kou

Time: May 20, 2:00pm – 3:00pm.

Location: Room 105, H2 Building


Spintronics, which utilizes both the charge/electric and the spin/magnetic properties, offers opportunities for a new generation of devices, which do not require the continuous application of a voltage to retain their information (i.e., nonvolatility). Hence, the spintronics devices enable extremely low standby power, and allow for integration of memory and logic functions at a more fundamental level. Moreover, in novel hybrid CMOS-spintronic computing architectures, by eliminating the need to transfer data back and forth from/to power-hungry and slow external magnetic memories, the system performance would be greatly improved, thus allowing for an instant on/off capability.

In this talk, I will briefly overview the recent emerging field of spintronics which utilize the spin-orbit coupling (SOC). The presence of large SOC can render a semiconductor to a topological insulator exhibiting Dirac electron surface states with the spin-momentum lock property. When magnetic order is introduced into topological insulators (TIs), the time-reversal-symmetry (TRS) is broken, and the non-trivial topological surface is driven into a new massive Dirac-fermions state. By controlling the magnetic (Cr) doping concentration and the Fermi level position, we show that the quantum anomalous Hall effect (QAHE) in the macroscopic millimeter-size magnetic-doped TI films. Furthermore, we find that the stability of the dissipationless chiral edge conductance is well-maintained as the film thickness varies across the 2D hybridization limit.

In the meanwhile, TI/Cr-doped TI heterostructures can also be used for the electrical manipulation of magnetization switching via giant spin–orbit torque (SOT). Therefore, in the second part of my talk, I will present our recent progress that the SOT required for magnetization switching in such magnetic TI-based bilayer structures is found to be three orders of magnitude more efficient than that of heavy metals.  All these exotic magnetic TI-based phenomena will serve as fundamental steps to further explore the TRS-breaking TI systems.  In addition, potential applications of energy efficient electronics will be discussed.


Xufeng Kou received his BS degree (with honor) in Chu Kochen Honors College and Optical Engineering from Zhejiang University (2009). From 2009 to 2015, he received his MS and PhD degrees in Electrical Engineering from University of California, Los Angeles (UCLA), under the direction of Raytheon Chair Professor Kang L. Wang. After receiving post-doc training at UCLA, Xufeng Kou joined SIST of ShanghaiTech University since February 2016. His current research interest includes novel semiconductors (topological insulators and dilute magnetic semiconductors) and their nano-electronics/spintronics applications. So far, Xufeng has co-authored 43 peer-reviewed journal papers including Nature Mater, Nature Nano., Nature Comm., Phys. Rev. Lett., Nano Lett., J. Amer. Chem. Soc., ACS Nano., and Proc. Natl. Acad. Sci., with more than 1300 citations (h-index of 21). He also holds several awards including the Qualcomm Innovation Fellowship (2012), Chinese Outstanding Student Abroad Scholarship (2013), and UCLA Distinguished PhD Dissertation Award (2015).


SIST-Seminar 16036