The normal liquid 3He conforms to Landau’s Fermi liquid picture but only at very low temperature. We have recently shown that the available experimental data can be accounted for assuming that the thermal conductivity is the sum of two contributions: one by quasi-particles (varying as the inverse of temperature) and another by a hydrodynamic sound mode (following the square root of temperature). The first component has been known for decades. The second is zero sound in the hydrodynamic limit [2]. The importance of a short wavelength sound mode was anticipated by early works on weak crystallization [3] and 2kF rotons [4]. We will discuss its role in the transport properties of metallic Fermi liquids whose resistivity displays a quadratic temperature dependence at low T [5] and consequences for the `strange metal’ [6] problematic.
[1] K. Behnia & K. Trachenko, Nature Commun. 15, 1771 (2024).
[2] F. Albergamo et al., Phys. Rev. Lett. 99, 205301 (2007).
[3] S. A. Brazovskii, J. Exp. Theor. Phys. 41, 85 (1975).
[4] A. M. Dyugaev, J. Exp. Theor. Phys. 43, 1247 (1976).
[5] K. Behnia, Annalen der Physik, 534, 2100588 (2022).
[6] P. W. Phillips, N. E. Hussey & P. Abbamonte, Science 377, eabh4273 (2022).