Hydrodynamic behavior of non-interacting quantum particles in presence of dephasing

In solids and organic materials, environment-induced dephasing of particles and long-lived excitations leads to the crossover in their transport properties between quantum wave-like propagation and classical diffusive motion. In this work, we demonstrate that dynamics of single carriers in this intermediate crossover regime can exhibit distinct signatures such as the formation of vortices and viscous flow, the phenomena typically considered as manifestations of hydrodynamic transport. We explain this effect by modeling suppressed quantum interference of carriers, and we show that the resulting dynamics resembles the linearized Navier-Stokes equations. Dephasing-assisted viscosity provides a potential alternative explanation of the results of recent experiments exhibiting hydrodynamic behavior in solids, and suggests experimental probes of how quantum carriers couple to their environment.