Inverse thermodiffusion of active matter in temperature gradient systems

Abstract

We have revealed an inverse thermodiffusion phenomenon for active particles under temperature gradient in one-species systems. This counterintuitive behavior is supported by numerical calculations as well as theoretical analyses. It is presented that the active particles flow from high-temperature to low-temperature regions when the self-driving force is small. On the contrary, the active particles can flow from low-temperature to high-temperature regions as long as the self-driving force is large enough. The mass current reversal phenomenon can be explained analytically from the special swimming pressures of the active particles. The P é clet numbers defined in our work indicate a potential application in separating the particles with different activities. The findings may bring a new understanding of the physical properties of active matter and provide enlightenment for the study of the non-equilibrium collective transport of active particles.