时　间：10月21日上午9:30

地　点：科技创新大楼C501

报告人：Prof. Bruce D. McCombe

报告题目：What's the g-factor in Narrow-gap-semiconductor Nanostructures?

Abstract:

B.D.McCombe is a professor of Physics in The State University of New York at Buffalo. Spin effects in semiconductors have received a great deal of attention for well over a decade, in the context of Spintronics technology, which focuses on controlling intrinsic spin (rather than charge) of carriers in semiconductors to produce new/novel functionalities for faster and lower power integrated circuits.  Manipulating spins is facilitated in materials having large Spin-Orbit interaction, which permits electric fields to be used for this purpose.  He will provide some background and summarize the basic physics and ideas, and then describe their recent studies of the electron g-factor and its anisotropy in two samples having so-called “composite channels” in the InAs/InGaAs/InAlAs heterostructure system. They have measured the spin-splitting of two-dimensional electrons in Landau Levels at low temperatures and in magnetic fields up to 10 T by magneto-transport and THz magneto-photoconductivity. Both the magnitudes of the experimental g-factors with the field along the quantization axis and their anisotropies (ratio of g-factor with B parallel to that with B perpendicular to the quantization axis) are at least a factor of two larger than the corresponding calculated single particle values.  They find that the many-body exchange contribution and its angular dependence (proportional cos θ, with θ the tilt angle) must be taken into account to understand this behavior.  In addition, we find evidence for an apparent vanishing of the exchange contribution at large tilt angles for the high mobility sample. The low mobility sample shows the expected cos θ dependence.  He will provide some insight into this behavior based on recent theoretical work.

Work supported in part by NSF-MWN 1008138