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TT: Fachverband Tiefe Temperaturen

TT 63: Focus Session: Emerging Magnetic Phenomena from Chiral Phonons I (joint session MA/TT)

TT 63.2: Invited Talk

Thursday, March 21, 2024, 10:00–10:30, H 1058

Chiral phonons in quantum materials revealed by the thermal Hall effect — •Gael Grissonnanche — Ecole Polytechnique, Palaiseau, France

It is becoming surprisingly clear that phonons can produce a large thermal Hall effect across a wide range of quantum materials, from cuprate superconductors [1,2] to titanates [3], iridates [4], and frustrated magnets [5]. The thermal Hall effect represents the deflection of a heat current by a perpendicular magnetic field. It is usually interpreted as coming from mobile hot electrons deflected by the Lorentz force. While trivial in metals, this effect is now found in insulators, and phonons that carry no charge are responsible for it. Phonons are the most common low-energy excitations in solids. Yet the handedness they acquire in a magnetic field * which triggers the thermal Hall effect * remains an enigma. In this talk, I will present the results that have led to the emergence of a new field of research aimed at discovering the origin of the thermal Hall effect of phonons and how this might relate to the question of chiral phonons measured by other probes.

[1] Grissonnanche et al. Nature 571, 376 (2019) [2] Grissonnancheet al. Nat. Phys. 16, 1108 (2020) [3] Li et al. Phys. Rev. Lett. 124, 105901 (2020) [4] Ataei et al. Nat. Phys. (2023) [5] Lefrançois et al. Phys. Rev. X 12, 021025 (2022)

Keywords: thermal Hall effect; chiral phonons; cuprates; superconductors; quantum spin liquids