Complex wave vector band structure for quantum transport

复波矢能带量子输运理论

Department of Physics and the Quantum Theory Project, University of Florida, Gainesville, FL 32611

Prof. Xiaoguang Zhang received his Ph.D in 1989 from Northwestern University. After that Prof. Zhang worked in Lawrence Berkeley Laboratory , University of Kentucky, and then in 1993 moved to Oak Ridge National Laboratory, eventually becoming a senior research staff member. Prof. Zhang joined Department of Physics and the Quantum Theory Project, University of Florida in 2014.Prof. Zhang is an expert on theory and calculation of condensed matter physics. His research interest covers (1) Theory and modeling of electron transport in magnetic tunnel junctions, molecular junctions, polymers and nanoscale materials, (2) Calculation of electron mobility and defect capture cross section in semiconductors, and (3) Image informatics for scanning tunneling potentiometry.

Abstract:Quantum mechanically forbidden states in a solid can exist as exponentially decaying states at surfaces and interfaces. These decaying states are described by complex wave vectors whose imaginary parts determine their rates of decay. The energy dependence of these complex wave vectors for a solid, the so-called complex band structure, can help us determine quantum transport properties of the material entirely from first-principles (i.e., without adjustable parameters that are fit to experiments). Complex band structure calculation was instrumental in the successful prediction of giant tunneling magnetoresistance in magnetic tunnel junctions. Here we show how complex band calculations can be extended 1. to predict negative differential resistance in magnetic tunnel junctions with narrow gap barrier layers, specifically those using so-called cubic cation disordered crystals (CCDC’s); 2. to estimate resistance of twin grain boundaries in copper; and 3. to calculate electron mobility in silicon due to impurity and phonon scattering. Comparison with experiments in cases 2 and 3 shows that complex band structure provides a powerful and accurate method for quantum transport.

时间：2016 年 5 月24 日下午2 :45

地点：yl6809永利官方版物理馆 323 阶梯教室