Prof. Shengjun Yuan
Institute for Molecules and Materials
Radboud University of Nijmegen, the Netherlands
时 间：7月30日（星期三）上午10点
地 点：唐仲英楼A313
摘 要：One of the most important problems in graphene and other 2D materials is to understand the influence of disorder on its physical properties. Motivated by recent experiments, we performed a systemic study of the electronic, optical and transport properties of single-layer, multilayer and nanostructured graphene by using the newly developed tight-binding propagation methods (TBPM). We consider systems consisting of multimillion-to-billion atoms, and study the effect of different types of disorder such as vacancies, adatoms, admolecules, ripples, puddles, coulomb impurities, grain boundaries, etc. The numerical methods are based on the wave propagation of electron according to the time-dependent Schrödinger equation, and applied in the calculations of following quantities: density of states, static and dynamic (optical) conductivity, quasieigenstates, polarization function, dielectric function, response function, energy loss function, collective modes, plasmon damping rate, diffusion coefficients, mean free path, localization length, electron velocity and mobility, magnetic susceptibility, quantum capacitance, tunneling probability, and Seebeck coefficient. The magnetic field is introduced by means of the Peierls substitution and the effect of electron-electron interaction is considered within the random phase approximation. The methods can be generalized to study the electron-phonon interactions and thermal conductivity. The computational effort of the calculation increases only linearly with the system size, and the numerical methods are applied also to the materials with multi-orbital Hamiltonian, such as graphane, fluorographene, boron nitride, transition metal dichalcogenides (e.g., MoS2 and WS2), black phosphorus, 2D and 3D topological insulators.
个人简介：Dr. Shengjun Yuan is a tenure-track assistant professor at Radboud University of Nijmegen, the Netherlands. He graduated from the Department of Physics at Zhejiang University in 2001, received his MSc. degree in theoretical physics from University of Siegen (Germany) in 2003, and received his PhD degree in computational physics from University of Groningen (The Netherlands) in 2008, for work on relaxation and decoherence in quantum spin systems. From 2009, he joined Theory of Condensed Matter group headed by Prof. M. I. Katsnelson at Radboud University of Nijmegen, and developed a series of new numerical methods in the modeling of graphene and other 2D materials. He has published more than 30 papers with total citations about 1000 times. His current research interests include the development of new numerical methods in the large-scale simulation of quantum systems; electronic, optical and transport properties of 2D materials; relaxation and decoherence in strong-correlated quantum spin systems.