Hot Particles Attract in a Cold Bath

Abstract

Controlling interactions out of thermodynamic equilibrium is crucial for designing addressable and functional self-organizing structures. These active interactions also underpin collective behavior in biological systems. Here we study a general setting of active particles in a bath of passive particles, and demonstrate a novel mechanism for long range attraction between active particles. The mechanism operates when the translational persistence length of the active particle motion is smaller than the particle diameter. In this limit, the system reduces to particles of higher diffusivity ("hot" particles) in a bath of particles with lower diffusivity ("cold" particles). This attractive interaction arises as a hot particle pushes cold particles away to create a large hole around itself, and the holes interact via a depletion-like attraction. Strikingly, the interaction range is more than an order of magnitude larger than the particle radius, well beyond the range of conventional depletion force. Although the mechanism occurs outside the parameter regime of typical biological swimmers, the mechanism could be realized in the laboratory.

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• Approach to equilibrium and non-equilibrium stationary distributions of interacting many-particle systems that are coupled to different heat baths
• Correlations in multithermostat Brownian systems with Lorentz force
• Demixing of active particles in the presence of external fields
• Long-time diffusion and energy transfer in polydisperse mixtures of particles with different temperatures
• Three-body problem for Langevin dynamics with different temperatures
• Diffusion of a tracer in a dense mixture of soft particles connected to different thermostats
• Dynamics and steady states of a tracer particle in a confined critical fluid
• Rectification in a mixture of active and passive particles subject to a ratchet potential
• Demixing of two species via reciprocally concentration-dependent diffusivity
• A Cold Tracer in a Hot Bath: In and Out of Equilibrium
• Statistical mechanics of a cold tracer in a hot bath
• Boundary-Induced Drift and Negative Mobility in Constrained Stochastic Systems