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Journal Articles Nature Communications Year : 2024

How heat propagates in liquid 3He

Abstract

Abstract In Landau’s Fermi liquid picture, transport is governed by scattering between quasi-particles. The normal liquid 3 He conforms to this picture but only at very low temperature. Here, we show that the deviation from the standard behavior is concomitant with the fermion-fermion scattering time falling below the Planckian time, $$\frac{\hslash }{{k}_{{{{{{{{\rm{B}}}}}}}}}T}$$ ℏ k B T and the thermal diffusivity of this quantum liquid is bounded by a minimum set by fundamental physical constants and observed in classical liquids. This points to collective excitations (a sound mode) as carriers of heat. We propose that this mode has a wavevector of 2 k F and a mean free path equal to the de Broglie thermal length. This would provide an additional conducting channel with a T 1/2 temperature dependence, matching what is observed by experiments. The experimental data from 0.007 K to 3 K can be accounted for, with a margin of 10%, if thermal conductivity is the sum of two contributions: one by quasi-particles (varying as the inverse of temperature) and another by sound (following the square root of temperature).

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Dates and versions

hal-04486443 , version 1 (01-03-2024)

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Kamran Behnia, Kostya Trachenko. How heat propagates in liquid 3He. Nature Communications, 2024, 15 (1), pp.1771. ⟨10.1038/s41467-024-46079-0⟩. ⟨hal-04486443⟩
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