报告题目: Large-scale GPU simulations of heat and charge transport in graphene
报告人: Zheyong Fan（樊哲勇）, Aalto University
Atomistic simulations can provide valuable theoretical understandings to experimental results, and in many situations, large-scale simulations are required to obtain reliable results. We have developed GPU (Graphics Processing Units) codes for both heat and charge transport simulations, based on classical molecular dynamics (MD) and quantum mechanical Kubo formalisms, respectively. Both codes have achieved excellent performance and have found a few interesting applications. Using the MD code, we have studied systematically heat transport in graphene. We proposed a new formalism which can distinguish the contributions to the total heat conductivity from the in-plane and the out-plane phonons. It is found that the out-of-plane component has much larger relaxation time and contributes about 2/3 of the total heat conductivity in pristine graphene. Results from equilibrium MD simulations are also found to agree with those from nonequilibrium MD simulations excellently. We have also studied the effects of isotopes, point-like defects, grain boundaries, external strain, substrate, etc. Using both codes, we have studied the influence of thermal ripples in suspended pristine graphene on the electronic transport properties. Contrary to the assumptions of continuous models, we found that the disorder for charge carriers induced by thermal ripples are short-ranged, and the transport fingerprints of the ripple-related disorder are very different from those of charged impurities. Our results indicate that thermal ripples are not likely the dominant source of disorder for charge carriers in graphene below room temperature.