Flocking from a quantum analogy: Spin-orbit coupling in an active fluid

Abstract

Systems composed of strongly interacting self-propelled particles can form a spontaneously flowing polar active fluid. The study of the connection between the microscopic dynamics of a single such particle and the macroscopic dynamics of the fluid can yield insights into experimentally realizable active flows, but this connection is well understood in only a few select cases. We introduce a model of self-propelled particles based on an analogy with the motion of electrons that have strong spin-orbit coupling. We find that, within our model, self-propelled particles are subject to an analog of the Heisenberg uncertainty principle that relates translational and rotational noise. Furthermore, by coarse-graining this microscopic model, we establish expressions for the coefficients of the Toner-Tu equations---the hydrodynamic equations that describe an active fluid composed of these "active spins." The connection between self-propelled particles and quantum spins may help realize exotic phases of matter using active fluids via analogies with systems composed of strongly correlated electrons.

13 pages, 3 figures

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Cited by in corpus (8)

• From a microscopic inertial active matter model to the Schrödinger equation
• Activity-induced phase transition in a quantum many-body system
• Engineering active motion in quantum matter
• Diffraction and interference with run-and-tumble particles
• Order by disorder: saving collective motion from topological defects in a conservative model
• Anisotropic run-and-tumble-turn dynamics
• Inertial Spinner Swarm Experiments: Spin Pumping, Entropy Oscillations and Spin Frustration
• Heat-to-motion conversion for quantum active matter