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学术报告

日期: 2017-08-23     阅读次数:89

报告题目:Quantum Thermal Fluctuation: from Casimir Force to Heat Transfer
报告人:Dr. Rongkuo Zhao, 加州大学伯克利分校
报告时间:2017年8月24日下午2点
报告地点:本部逸夫楼现代光学技术研究所3楼会议室

报告摘要: 
To obtain more capabilities, devices are becoming smaller and smaller. Because nanostructures are extremely sensitive to undesirable forces and heat, managing force and controlling heat represent the biggest challenge in nanoscale mechanics and heat management. Quantum thermal fluctuation induced electromagnetic fields result in attractive forces between closely spaced electrically neutral surfaces, called Casimir force. The fluctuation induced charges can behave as optical antennas which can emit light and carry thermal energy from one object to another through vacuum gaps. The lateral component of Casimir interactions has been predicted to provide frictional forces between two non-contact surfaces. 
For two surfaces of the same material, Casimir force is intrinsically always monotonically attractive, which results in disaster of unavoidable adhesion and friction in micro-/nano- machines. In my talk, I will focus on my recent theoretical and experimental demonstration of stable Casimir equilibia, where the Casimir force between two surfaces is repulsive at distances smaller than several tens of nanometers and attractive at large distances so that the components in nanomachines can remain noncontact and stably trapped at a controllable distance. 
Casimir forces are predicted to play a dominant role on thermal energy transfer through a sub-nanometer vacuum gap. However, at such a scale, other forces like Coulomb force and chemical bonding between two surfaces can also play a role and the tunneling electrons and photons also carry energy from one to another. Considering the tiny sub-nanometer separation, experimental verification of these mixed hypotheses is extremely challenging. In this talk, I will also talk about experimental observation of thermal energy transfer mediated by Casimir forces through a micrometer vacuum gap. 
The existence of quantum friction is still under debate. However, all theoretical studies so far are extremely difficult to verify in experiment. At the end, I will theoretically propose a model system for observing this quantum phenomenon.

报告人简介:
Rongkuo Zhao is a postdoctoral scholar in the laboratory of Xiang Zhang in Nanoscale Science and Engineering Center and Department of Mechanical Engineering at University of California, Berkeley. Prior to his current position, he was a Royal Commission for the Exhibition of 1851 Research Fellow in John Pendry’s group in Department of Physics at Imperial College London in the UK. He completed his BS degree in Applied Physics in 2007 at Xi’an Jiaotong University, China. He received his Ph.D. degree in Optics from Beijing Normal University in 2011, co-supervised by Dahe Liu in China and Costas Soukoulis at Iowa State University. His research interests are in quantum and thermal ?uctuation-induced electromagnetic interactions including van der Waals and Casimir forces, noncontact quantum friction, and radiative heat transfer, and also in understanding the interaction of light with artificial nanostructures such as metamaterials, plasmonics, and photonic crystals.



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