Single-File Diffusion of Active Brownian Particles

Single-file diffusion (SFD) is critical to understanding transport phenomena across various physical and biological systems. The hallmark of SFD is the confinement of microscopic particles to a narrow channel where they cannot pass one another, resulting in highly restricted motion and leading to anomalous diffusion. This study uses Brownian dynamics simulations and analytical theory to investigate the SFD of active Brownian particles (ABPs). Through scaling relations and heuristic arguments, we derive an accurate analytical expression for a tagged ABP's mean square displacement (MSD). Our analysis captures both the MSD's short- and long-time behaviors, providing insights into how particle activity and system density influence these regimes. The MSD exhibits ballistic behavior at short times, which we quantitatively relate to the reduced kinetic temperature of the single-file ABP system. We also find that while the characteristic subdiffusive scaling of SFD [〈△x² 〉∼ t^1/2] is preserved at long times, self-propulsion introduces significant modifications to the 1D-mobility, which can be directly related to the constant Péclet (Pe) compressibility. Furthermore, we demonstrate that the generalized 1D-mobility, initially proposed by Kollmann for equilibrium systems [Phys. Rev. Lett. 90, 180602 (2003)], can be extended to active systems with minimal modification. These findings have important implications for designing microfluidic systems and provide a basis for understanding active matter in geometries with highly restricted motion.