时间：2013年5月10日上午11：00-12：30
地点：北京大学深圳研究生院G-205
主办方：新材料学院
报告题目：Electronic transport through silicon nanostructures based on orbital-free DFT and non-equilibrium Green’s function
报告人：Fuming Xu, Department of Physics, The University of Hong Kong
Tittle:Electronic transport through silicon nanostructures based on orbital-free DFT and non-equilibrium Green’s function
Speaker:Fuming Xu, Department of Physics, The University of Hong Kong
Abstract: Orbital-free density functional theory (OFDFT) replaces the wavefunction in the kinetic energy by an explicit energy functional and thereby speeds up significantly the calculation of ground state properties of the solid state systems. So far, the application of OFDFT has been centered on closed systems and less attention is paid on the transport properties in open systems. In this talk, I will show our recent work, which combines OFDFT with non-equilibrium Green's function (NEGF) to simulate equilibrium electronic transport properties in nanostructures from first principles. In particular, we study ac transport properties of a silicon atomic junction consisting of a silicon atomic chain and two monoatomic leads. We have calculated the dynamic conductance of this atomic junction as a function of ac frequency with one to four silicon atoms in the central scattering region. The system is found to be capacitive-like in the finite frequency regime. Our analysis shows that, up to 0.1 terahertz(THz), this behavior can be characterized by a classic RC circuit consisting of two resistors and a capacitor. One resistor gives rise to dc resistance and the other one accounts for the charge relaxation resistance. The OFDFT-NEGF formalism demonstrates many advantages such as low computational cost and stable convergence, which are essential in ab initio modeling of large-scale nanostructures.
Besides, I would like to briefly introduce the Nanodsim software in this talk. The Nanodsim is based on NEGF-DFT theory, but the coherent potential approximation (CPA) and nonequilibrium vertex correction (NVC) make it a powerful tool in modeling disorder averaging problem from atomic principles. Two topics will be given to show its potential application in material developing field. One is the bandgap issue in doped semiconductor materials and the other is its performance in solving large size problem.
About the speaker: Xu received his Bachelor degree in Science from Shanxi University in 2006. After that, he went to Department of Physics, The University of Hong Kong to continue his postgraduate study. Xu obtained the degree of Doctor of Philosophy in Condensed Matter Physics in 2011. Then he joined the Area of Excellence: ‘Theory, Modeling, and Simulation of Emerging Electronics’ research program as a postdoctoral fellow. Xu’s research works include universal statistical behavior of mesoscopic systems, NEGF-DFT simulation of electronic transport in nanostructures, and development of OFDFT in open systems, etc. He also has research interest in the transport properties of new emerging materials, such as MoS2 and silicene, and first principle modeling of disorder scattering problems in nanoscale systems using nanodsim software.
