Events

Next Quantum Material Seminar:

Thursday, March 2nd 2023 at 2:00 pm

Kamran Behnia  (ESPCI)

“ Thermal transport and quasi-particle hydrodynamics”

To access this seminar:

Institut Néel CNRS, Building D, Room Nevill Mott  (D420)

Abstract: Heat travels in solids thanks to mobile electrons and phonons. Even in a detect-free solid, due to the presence of the lattice, collisions degrade the flow. However, there are situations where a significant fraction of collisions conserve momentum. In this hydrodynamic regime, the quasi-particle viscosity becomes significant. In a variety of insulators such as strontium titanate [1], black phosphorus [2], or graphite [3], there is a narrow temperature window where momentum-conserving collisions between phonons enhance thermal diffusivity. Interestingly, both black phosphorus and strontium titanate also display a thermal Hall effect [4], whose origin is yet to be identified.

In the case of semi-metallic antimony, where each electron and each hole are shared by a thousand atoms, the most frequent colliders of phonons at cryogenic temperatures are electrons (and not other phonons, defects or boundaries). This is an electron-phonon bi-fluid [5] with dissymmetric exchange. There is a leak for phonon energy energy flow through collisions by electrons, but the electron flow does not suffer by phonon scattering. As a consequence, phonons do not become ballistic, and the electronic T-square resistivity [6] is driven by transmission and absorption of acoustic phonons.  

[1] V. Martelli et al., Phys. Rev. Lett. 120, 125901 (2018) 
[2] Y. Machida et al., Sci. Adv.  4, eaat3374 (2018) 
[3] Y. Machida et al., Science 367, 309 (2020) 
[4] X. Li et al., Phys. Rev. Lett. 124, 105901 (2022)
[5] A. Jaoui et al. Physical Review X 12, 031023 (2022) 
[6] A. Jaoui et al., Nature Communications 12, 195 (2021)

The organizers:

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)