Energy Transport in Extreme Thermal Materials

Yongjie Hu, UCLA

Controlling thermal transport is critical for many applications including electronics and energy systems. Discovering new structures with extreme thermal properties will not only enable disruptive technologies, but also provide platforms to develop fundamental understandings beyond the boundary of classical theories. In this talk, I will first describe our recent effort in discovering new compound materials with ultrahigh thermal conductivity, above all common semiconductors and metals [1,2]. We performed ultrafast optical spectroscopy to quantify the unique band structures and phonon mean free path spectra. Through self-assembled design and manufacturing, we were able to demonstrate high performance electronics thermal management beyond the state of the art [3]. On the other hand, we investigated ultralow thermal conductivity materials with high thermoelectric energy efficiency. Examining the intrinsic crystals of 2D van der Waals materials, we observed abnormally strong phonon renormalization at room temperature due to high order phonon anharmonicity, as well as the failure of widely used quasi-harmonic model in the calculation of thermophysical properties [4,5]. Moreover, we conducted ab initio atomistic calculations and theoretically predicted a new group of candidate structures with extreme conductivity [6,7].

References:

[1] Science 361, 575 (2018).

[2] Nano Letters 17, 7507 (2017).

[3] Nature Communications, in press (2021).

[4] Nano Letters 19, 4941 (2019)

[5] Advanced Materials 31, 1901021 (2019).

[6] Phys. Rev. B 100, 085420 (2019).

[7] Phys. Rev. B 103, L041203 (2021).

BIOSKETCH: Yongjie Hu is an Associate Professor of Mechanical and Aerospace Engineering at UCLA. His group exploits interdisciplinary experimental and theoretical approaches to investigate new materials, spectroscopy transport mechanisms, and device applications. Before joining the faculty of UCLA, he received Ph.D. from Harvard University and Battelle-MIT postdoctoral fellowship from MIT. His research has been recognized by diverse research societies including the Sloan Research Fellow, ASME Bergles-Rohsenow Young Investigator Award in Heat Transfer, NSF CAREER Award, US Air Force Young Investigator Award, ACS PRF Doctoral New Investigator Award, and the UCLA Watanabe Excellence in Research Award.

https://rochester.zoom.us/j/92285380512?pwd=bUZOYTBBWHhMUHFRY1B5Z09jeHJ6dz09

Meeting ID: 922 8538 0512

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