Current reversal in polar flock at order-disorder interface

TL;DR

This study investigates the behavior of polar self-propelled particles in a three-region system with varying noise levels, revealing a current reversal phenomenon at the interface that could inform active device design.

Contribution

It introduces a novel system geometry inspired by Josephson Junctions to analyze SPPs, discovering current reversal due to interface randomness.

Findings

Current reversal occurs at intermediate interface widths.

System transitions from order to disorder with increasing interface size.

Interface randomness causes reflection and current reversal.

Abstract

We studied a system of polar self-propelled particles (SPPs) on a thin rectangular channel designed into three regions of order-disorder-order. The division of the three regions is made on the basis of the noise SPPs experience in the respective regions. The noise in the two wide region is chosen lower than the critical noise of order-disorder transition and noise in the middle region or interface is higher than the critical noise. This make the geometry of the system analogous to the Josephson Junction (JJ) in solid state physics. Keeping all other parameters fixed, we study the properties of the moving SPPs in the bulk as well as along the interface for different widths of the junction. On increasing interface width, system shows a order-to-disorder transition from coherent moving SPPs in the whole system to the interrupted current for large interface width. Surprisingly, inside the interface we observed the current reversal for intermediate widths of the interface. Such current reversal is due to the strong randomness present inside the interface, that makes the wall of the interface reflecting. Hence Our study give a new interesting collective properties of SPPs at the interface which can be useful to design devices like switch using active agents.