arXiv subjects

C. W. Wächtler

Publications and source records attributed to C. W. Wächtler.

6 recordsLinked to original sources

arXiv2020

Dissipative nonequilibrium synchronization of topological edge states via self-oscillation

The interplay of synchronization and topological band structures with symmetry protected midgap states under the influence of driving and dissipation is largely unexplored. Here we consider a trimer chain of electron shuttles, each consisting of a harmonic oscillator coupled to a quantum dot positioned between two electronic leads. Each shuttle is subject to thermal dissipation and undergoes a bifurcation towards self-oscillation with a stable limit cycle if driven by a bias voltage between the leads. By mechanically coupling the oscillators together, we observe synchronized motion at the ends of the chain, which can be explained using a linear stability analysis. Due to the inversion symmetry of the trimer chain, these synchronized states are topologically protected against local disorder. Furthermore, with current experimental feasibility, the synchronized motion can be observed by measuring the dot occupation of each shuttle. Our results open a new avenue to enhance the robustness of synchronized motion by exploiting topology.

quant-ph↗

arXiv2020

Transport through a quantum critical system: A thermodynamically consistent approach

Currents through quantum systems may probe non-analyticities in quantum-critical many-body ground states. For a large class of dissipative quantum critical systems we show that it is possible to obtain the reduced system dynamics in the vicinity of quantum critical points in a thermodynamically consistent way, while capturing non-Markovian effects. We achieve this by combining reaction coordinate mappings with polaron transforms. Exemplarily, we consider the Lipkin-Meshkov-Glick model in a transport setup, where the quantum phase transition manifests itself in the heat transfer statistics.

cond-mat.stat-mech↗

arXiv2019

Proposal of a realistic stochastic rotor engine based on electron shuttling

We propose and analyse an autonomous engine, which combines ideas from electronic transport and self-oscillating heat engines. It is based on the electron-shuttling mechanism in conjunction with a rotational degree of freedom. We focus in particular on the isothermal regime, where chemical work is converted into mechanical work or vice versa, and we especially pay attention to use parameters estimated from experimental data of available single components. Our analysis shows that for these parameters the engine already works remarkably stable, albeit with moderate efficiency. Moreover, it has the advantage that it can be up-scaled to increase power and reduce fluctuations further.

cond-mat.stat-mech↗

arXiv2019

Stochastic thermodynamics of self-oscillations: the electron shuttle

Self-oscillation is a phenomenon studied across many scientific disciplines, including the engineering of efficient heat engines and electric generators. We investigate the single electron shuttle, a model nano-scale system that exhibits a spontaneous transition towards self-oscillation, from a thermodynamic perspective. We analyze the model at three different levels of description: The fully stochastic level based on Fokker-Planck and Langevin equations, the mean-field level, and a perturbative solution to the Fokker-Planck equation that works particularly well for small oscillation amplitudes. We provide consistent derivations of the laws of thermodynamics for this model system at each of these levels. At the mean-field level, an abrupt transition to self-oscillation arises from a Hopf bifurcation of the deterministic equations of motion. At the stochastic level, this transition is smeared out by noise, but vestiges of the bifurcation remain visible in the stationary probability density. At all levels of description, the transition towards self-oscillation is reflected in thermodynamic quantities such as heat flow, work and entropy production rate. Our analysis provides a comprehensive picture of a nano-scale self-oscillating system, with stochastic and deterministic models linked by a unifying thermodynamic perspective.

cond-mat.stat-mech↗

arXiv2016

Stochastic thermodynamics based on incomplete information: Generalized Jarzynski equality with measurement errors with or without feedback

In the derivation of fluctuation relations, and in stochastic thermodynamics in general, it is tacitly assumed that we can measure the system perfectly, i.e., without measurement errors. We here demonstrate for a driven system immersed in a single heat bath, for which the classic Jarzynski equality $\langle e^{-β(W-ΔF)}\rangle = 1$ holds, how to relax this assumption. Based on a general measurement model akin to Bayesian inference we derive a general expression for the fluctuation relation of the measured work and we study the case of an overdamped Brownian particle and of a two-level system in particular. We then generalize our results further and incorporate feedback in our description. We show and argue that, if measurement errors are fully taken into account by the agent who controls and observes the system, the standard Jarzynski-Sagawa-Ueda relation should be formulated differently. We again explicitly demonstrate this for an overdamped Brownian particle and a two-level system where the fluctuation relation of the measured work differs significantly from the efficacy parameter introduced by Sagawa and Ueda. Instead, the generalized fluctuation relation under feedback control, $\langle e^{-β(W-ΔF)-I}\rangle = 1$, holds only for a superobserver having perfect access to both the system and detector degrees of freedom, independently of whether or not the detector yields a noisy measurement record and whether or not we perform feedback.

cond-mat.stat-mech↗

arXiv2016

Lane formation in a driven attractive fluid

We investigate non-equilibrium lane formation in a generic model of a fluid with attractive interactions, that is, a two-dimensional Lennard-Jones (LJ) fluid composed of two particle species driven in opposite directions. Performing Brownian Dynamics (BD) simulations for a wide range of parameters, supplemented by a stability analysis based on dynamical density functional theory (DDFT), we identify generic features of lane formation in presence of attraction, including structural properties. In fact, we find a variety of states (as compared to purely repulsive systems), as well as a close relation between laning and long wavelength instabilities of the homogeneous phase such as demixing and condensation.

cond-mat.soft↗