Thermoelectric signatures of the electron-phonon fluid in PtSn4

Abstract

In most materials, transport can be described by the motion of distinct species of quasiparticles, such as electrons and phonons. Strong interactions between quasiparticles, however, can lead to collective behaviour, including the possibility of viscous hydrodynamic flow. In the case of electrons and phonons, an electron-phonon fluid is expected to exhibit strong phonon-drag transport signatures and an anomalously low thermal conductivity. The Dirac semi-metal PtSn4 has a very low resistivity at low temperatures and shows a pronounced phonon drag peak in the low temperature thermopower; it is therefore an excellent candidate for hosting a hydrodynamic electron-phonon fluid. Here we report measurements of the temperature and magnetic field dependence of the longitudinal and Hall electrical resistivities, the thermopower and the thermal conductivity of PtSn4. We confirm a phonon drag peak in the thermopower near 14 K and observe a concurrent breakdown of the Lorenz ratio below the Sommerfeld value. Both of these facts are expected for an electron-phonon fluid with a quasi-conserved total momentum. A hierarchy between momentum-conserving and momentum-relaxing scattering timescales is corroborated through measurements of the magnetic field dependence of the electrical and Hall resistivity and of the thermal conductivity. These results show that PtSn4 exhibits key features of hydrodynamic transport.

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Cited by in corpus (10)

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• Hydrodynamic approach to two-dimensional electron systems
• Electron-phonon hydrodynamics
• Dynamo Effect and Turbulence in Hydrodynamic Weyl Metals
• Optical signatures of shear collective modes in strongly interacting Fermi liquids
• Formation of an electron-phonon bi-fluid in bulk antimony
• Hydrodynamic effective field theories with discrete rotational symmetry
• Hydrodynamics with triangular point group
• Critical Viscosity of a Fluctuating Superconductor
• Hydrodynamics of the electronic Fermi liquid: a pedagogical overview