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Seminar – Anomalous phonon/heat transport in low dimensional micro/nano materials – Dr. Baowen Li
September 22 @ 11:45 am - 12:45 pm
Rennie Family Endowed Professor
Department of Mechanical Engineering, University of Colorado, Boulder
When system dimension and size go down, many interesting phenomena can happen. Both experimental and numerical works in recent years have shown that phonon/heat transport in low (quasi 1D and 2D) dimensional nano structures like nanotube, nanowire, polymer chain, graphene, and other 2D materials show anomalous behavior:
(a) heat conduction due to phonons does not follow the Fourier law;
(b) heat transports may break down the reciprocal principle, namely heat flows asymmetrically.
(c) negative differential thermal resistance will arise, namely the larger the temperature drops, the smaller the heat current.
Issues (b) and (c) can be used to build up useful phononic thermal devices like thermal diode and thermal transistor, which lay the foundation of a new emerging field – phononics.
In this talk, I will focus on issue (a) and present a general theoretical understanding of the anomalous phonon/heat transport. More specifically, I will discuss how the anomalous thermal transport – a macroscopic phenomenon – is connected with the anomalous energy diffusion – a microscopic process.
V Lee et al Phys Rev Lett 118, 135901, (2017).
Dr. Li received B. S from Nanjing University, M. Sci from Institute of Acoustics, the Chinese Academy of Science, and Ph. D from Oldenburg University, Germany in 1985, 1989 and 1992, respectively. He joined National University of Singapore (NUS) as assistant professor in 2000, and become full professor in 2007 and worked there until 2014. He has been 2014/2015 Russell Severance Springer Professor at Department of Mechanical Engineering, UC Berkeley. In August 2015, he joined Department Mechanical Engineering, University of Colorado Boulder as the Rennie Family Endowed Professor.
He is one of the pioneers in an emerging field – Phononics. He has authored and co-authored 293 papers with more than 14,000 citations. Delivered more than 220 plenary, keynote, invited/seminar talks. He is APS fellow (2013), and recipient of numerous awards including 2005 National Science Award, Singapore, and 2005 OCPA’s (International Organization of Chinese Physicists and Astronomers) Asia Achievement Award and 2014/2015 Springer Professorship at University of California, Berkeley. 2015 Brillouin Medal from International Phononics Society.
His currently research activities include but not limited to: fundamental theory and measuring techniques of phonon/heat transport, phononic thermal devices, thermal metamaterials, topological phononics, nano structured thermoelectric materials, and complex networks etc.