BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Thermal transport beyond the Ioffe-Regel limit\, and resonances in
  heat hydrodynamics - Michele Simoncelli\, EPFL
DTSTART:20211101T163000Z
DTEND:20211101T170000Z
UID:TALK162325@talks.cam.ac.uk
CONTACT:Dr Christoph Schran
DESCRIPTION:Recently\, it has been shown that the two established heat con
 duction mechanisms—namely the propagation of\natomic vibrational waves i
 n anharmonic crystals elucidated by Peierls [1] and the couplings between 
 atomic vibrational modes in harmonic glasses envisioned by Allen and Feldm
 an [2]—naturally emerge as limiting cases of a unified theory\, derived 
 from the Wigner formulation of quantum mechanics and describing on an equa
 l footing solids ranging from crystals to glasses [3].\n\nHere\, we rely o
 n this unified theoretical framework to\ninvestigate what happens when ato
 mic vibrational waves reach the Ioffe-Regel limit (i.e. their mean free pa
 ths\nbecome shorter than the interatomic spacing)\, showing that they can 
 still contribute to heat transport due to\ntheir wave-like capability to i
 nterfere and tunnel. Then\, we focus on signatures of the “hydrodynamic
 ” regime of thermal transport\, where heat conduction becomes fluid-like
  and Fourier’s diffusive equation fails. We show that the recent observa
 tion of temperature waves in this regime [4] can be explained using the 
 “viscous heat equations” [5]\, thus we propose a strategy that uses re
 sonance to amplify these temperature waves.\n\n[1] R. Peierls\, Ann. Phys.
  395\, 1055–1101 (1929)\n\n[2] P. B. Allen and J. L. Feldman\, Physical 
 Review Letters 62\, 645–648 (1989)\n\n[3] M. Simoncelli\, N. Marzari\, a
 nd F. Mauri\, Nature Physics\, 15\, 809 (2019).\n\n[4] J. Jeong\, X. Li\, 
 S. Lee\, L. Shi\, and Y. Wang\, Physical Review Letters 127\, 085901 (2021
 )\n\n[5] M. Simoncelli\, N. Marzari\, and A. Cepellotti\, Physical Review 
 X 10 \, 011019 (2020).\n
LOCATION:Dept of Chemistry\, Wolfson Lecture Theatre and Zoom
END:VEVENT
END:VCALENDAR