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Next Quantum Material Seminar:


Thursday, March 2, 2pm

Kamran Behnia (ESPCI)




To access this seminar:

K223, Institut Néel, Building K 1st floor, Room  Remy Lemaire



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)


Next scheduled seminars are:

  • Thursday 19 January, 2pm: Frederic Bourdarot (CEA Grenoble)
  • Thursday 23 February, 2pm: Gediminas Simutis (PSI Switzerland)
  • Thursday 2 March, 2pm: Kamran Behnia (ESPCI)
  • Thursday 16 March, 2pm: Mikhail Feigel’man (LPMMC)


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The organizers:

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