  Hydrodynamic fluidity in condensed matter physics has been experimentally
demonstrated only in a limited number of compounds due to the stringent
conditions that must be met. Herein, we performed thermal and electrical
transport experiments in three-dimensional topological semimetal ZrTe5. By
measuring the thermal properties in a wide temperature range, two
representative experimental evidences of the hydrodynamics are observed in
temperature window between the ballistic and diffusive regimes: a faster
evolution of the thermal conductivity than in the ballistic regime and the
non-monotonic temperature-dependent effective quasiparticle mean-free-path. In
addition, magneto-thermal conductivity results indicate that charged
quasiparticles, as well as phonons, may also play an important role in this
hydrodynamic-like flow in ZrTe5.

Strongly Correlated Electrons