In the afternoon of April 28, the forum on the topic of "HUST-NUS academic lecture series" was successfully held in our school. Prof. Wang Jiansheng from the Department of Physics at NUS gave a lecture titled as "Energy, momentum, and angular momentum transfers mediated by photons". Over 100 domestic and foreign researchers participated in this forum online.
Prof. Wang said that black-body radiation and Casimir force are well-known. Black-body radiation is energy transfer, while Casimir force between metal plates is momentum transfer. Here, we consider N objects in vacuum each locally may in thermal equilibrium but globally in nonequilibrium steady state. Transport of energy, momentum, or angular momentum is then possible mediated by the electromagnetic fields. It is also useful to consider an extra N+1"object" which is the "bath-at-infinity" for conservation laws. General formulas of Meir-Wingreen type are derived based on the nonequilibrium Green's functions (NEGF) for the photon field and the Keldysh formalism. The materials properties are represented by self-energies. We illustrate the usefulness of the formulas and present some results of calculations, such as the angular momentum emission by a benzene ring driven by electric current, energy and angular momentum emission from a Haldane model of electrons, and also energy, momentum, and angular momentum emissions from graphene edges in nonequilibrium states.
The biography of the speaker is as followed:
Wang Jiansheng , the APS Fellow (2005), the professor of the Department of Physics, National University of Singapore. He received the Bachelor degree from Jilin University (China) in 1982, and PhD degree from Carnegie Mellon University (USA) in 1987. He has been working at the Department of Physics, National University of Singapore since 1993, previously acting as a Depute Head of the Department of Computational Science and Department of Physics. From 2004 to 2006, he was the Adjunct Professor at the School of Physics, HUST.
Prof. Wang is well-known for his work of using Monte Carlo simulation to solve problems in statistical mechanics. The Swendsen-Wang algorithm has been written into many textbooks of statistical physics and computational physics. His new book titled as "Advanced Statistical Mechanics" was published in 2022. In the past two decades, his research interest has shifted to quantum transport in nanostructures and the development of the nonequilibrium Green's function (NEGF) method. He has been working on thermal transport via molecular dynamics and NEGF, electron-phonon interactions, thermal Hall effect, quantum master equations in transport. In recent years, he focuses on the near-field radiative heat transfer, transport of angular momentum and Casimir force.
