Non-equilibrium thermodynamics of intermittent potentials following a telegraphic process

Abstract

Investigations on active systems, resetting protocols and dynamics in biological systems reveals description of observed phenomena as caused by fluctuating forces. In particular, we have observed telegraphic-like dynamics in active forces causing net rotation of ratchet gears in active baths [PRE 101, 022604 (2020)] and in traction forces induced by Physarum polycephalum resulting in active gels [Physica A 603, 127812 (2022)]. A critical step to elucidate the thermodynamics of systems under telegraphic forces is to measure their distance from equilibrium state at least in the steady state regime. We proposed a measure, K*, from a detailed-balance like relation to quantitatively measure this distance. We performed an experiment using a single optical trap to measure the dynamics of a probed particle with the trap being turned ON and OFF at some rate χ [PRE 104, 044609 (2021)]. We found that K*approaches zero at high switching rate corresponding to an equilibrium condition but with an effective spring constant much less than the experimental value. With inspiration from biology, we then consider the dynamics of probe particle in complex intermittent potential field. We performed experiments on a probe particle in an asymmetric quartic potential following a telegraphic process using a double optical tweezer set-up. We found the potential can be made symmetric at some switching rate. Moreover, non-linear dependence of the first passage time for barrier crossing to the switching rate was observed.