Magnetized granular particles running and tumbling on the circle S^{1}

Area of Science:

• Physics
• Active Matter Physics
• Granular Systems

Background:

• Nonvibrating magnetic granular systems driven by alternating magnetic fields display characteristics of active matter.
• Active matter systems are collections of self-propelled entities that exhibit complex collective behaviors.

Purpose of the Study:

• To investigate the dynamics of a simplified active matter system: a single magnetized spherical particle in a circular channel.
• To theoretically analyze the particle's motion using a run-and-tumble model and predict phase transitions.
• To experimentally validate the theoretical findings and explore the influence of particle magnetization.

Main Methods:

• Theoretical modeling using the run-and-tumble model applied to circular motion.
• Experimental setup involving a single magnetized spherical particle in a circular channel subjected to an alternating magnetic field.
• Analysis of particle motion to determine characteristic persistence length and identify dynamical phases.

Main Results:

• A dynamical phase transition was predicted and observed between an erratic (disordered) phase and a persistent (ordered) phase.
• The transition occurs when the characteristic persistence length (ℓc) relates to the channel radius (R) by ℓc = R/2.
• Smaller particle magnetization was found to correlate with a larger persistence length, consistent with theoretical predictions.

Conclusions:

• The single magnetic particle system effectively mimics active matter behavior.
• The run-and-tumble model accurately predicts the observed dynamical phase transition.
• Particle magnetization is a key factor influencing the transition between disordered and ordered motion in this system.