Activity driven transport in harmonic chains

Abstract

The transport properties of an extended system driven by active reservoirs is an issue of paramount importance, which remains virtually unexplored. Here we address this issue, for the first time, in the context of energy transport between two active reservoirs connected by a chain of harmonic oscillators. The couplings to the active reservoirs, which exert correlated stochastic forces on the boundary oscillators, lead to fascinating behavior of the energy current and kinetic temperature profile even for this linear system. We analytically show that the stationary active current (i) changes non-monotonically as the activity of the reservoirs are changed, leading to a negative differential conductivity (NDC), and (ii) exhibits an unexpected direction reversal at some finite value of the activity drive. The origin of this NDC is traced back to the Lorentzian frequency spectrum of the active reservoirs. We provide another physical insight to the NDC using nonequilibrium linear response formalism for the example of a dichotomous active force. We also show that despite an apparent similarity of the kinetic temperature profile to the thermally driven scenario, no effective thermal picture can be consistently built in general. However, such a picture emerges in the small activity limit, where many of the well-known results are recovered.

Dynamical fluctuations of a tracer coupled to active and passive particles

“…where Ω(t) is just an exponentially correlated colored noise, the same as the autocorrelation of the active particles of the environment. The form of ( 21) has been used in previous works [21,23,40], the emergence of the same from a microscopic model of active environment justifies these phenomenological models. Moreover, ( 21) is familiar with the equation of standard underdamped active particles.…”

“…Thus, providing an effective description of a system in a nonequilibrium environment is a problem highly sought-after. Moreover, transport properties of extended systems connected to active environments have also gained interest recently [21], and an accurate description of such environments has thus become very important. This is evident from the huge body of works involving experiments in microrheology and biophysics, whose main objective is to understand how the nonequilibrium features of the active environment are reflected on the dynamics of a tracer particle [10,16,[22][23][24][25][26][27][28][29][30][31][32].…”

Stationary state of harmonic chains driven by boundary resetting

“…The action of nonequilibrium reservoirs, which do not satisfy fluctuation-dissipation theorem (FDT) [11], on single probe particles leads to unusual features like anomalous relaxation dynamics, negative viscosity, modification of equipartition theorem, etc [12][13][14][15][16][17][18][19][20][21][22]. Recently, the NESS of a harmonic chain driven by active baths (nonequilibrium bath) is studied in [23,24]. Here we model a nonequilibrium reservoir using stochastic resetting.…”

“…When the boundary oscillators of a one-dimensional harmonic chain are attached to two of these reservoirs, the chain attains NESS with an average nonzero energy current flowing through the system due to the action of these reservoirs. The average energy current can be easily calculated from the formalism used in [23] and the value of the average energy current depends on the resetting rate of the boundary walls. We find that the velocity distribution of the bulk oscillator reaches the Gaussian distribution only at a thermodynamically large system size.…”

The Sun within: active processes from two-temperature models

“…The fact that energy transfer and the related possibility to deliver work need not be driven by differences in real temperature between thermal (equilibrium) baths has been noted before, e.g . in [3–7]; it suffices that the “effective” temperatures ( e.g . as calculated from the relative occupations in a multilevel system) between two regions are different.…”