Effective temperature defined by diffusivity and fluctuation of an active Brownian particle

This talk addresses an ongoing debate on whether effective temperature (T_eff) is a state function of an active colloid. The debate arises because effective temperatures (T_eff) defined by different dynamic variables may not be the same. We address this debate using active Brownian particles comprising metallic Janus particles driven by induced-charge electrophoresis. We determined T_eff1 from the ratio of the active diffusivity over the passive diffusivity. We also determined T_eff2 from the low-frequency limit of the noise power spectral density of an ABP in an optical trap. The T_eff1 and T_eff2 are found to be equal, both are linearly proportional to the drift speed squared, suggesting they are a state function for the ABP system.