Selected Topics:

Thermoelectric heat engine

Thermodynamics and Information

Self-propelled particle

Vesicles in flow

Membrane Adhesion

Hidden degree of freedom


 

Stochastic Thermodynamics

Extreme fluctuations of active Brownian motion

In active Brownian motion, an internal propulsion mechanism interacts with translational and rotational thermal noise and other internal fluctuations to produce directed motion. We derive the distribution of its extreme fluctuations and identify its universal properties using large deviation theory. The limits of slow and fast internal dynamics give rise to a kink-like and parabolic behavior of the corresponding rate functions, respectively. For dipolar Janus particles in two- and three-dimensions interacting with a field, we predict a novel symmetry akin to, but different from, the one related to entropy production. Measurements of these extreme fluctuations could thus be used to infer properties of the underlying, often hidden, network of states.

Related publications

Extreme fluctuations of active Brownian motion
P. Pietzonka, K. Kleinbeck, and U. Seifert
New J. Phys., 18, 052001, 2016
Abstract Download (pdf icon pdf)

 

Mesoscopic heat engines

Cyclic engine Ever since James Watt's steam engine, the urge to explore the fundamental principles governing the performance of devices that convert thermal energy into useful work was one of the major quests in thermodynamics. From a conceptual point of view, such heat engines can be divided into two classes. Cyclic engines use a reciprocating piston to generate mechanical work by periodically compressing and expanding a working fluid at varying temperature. Thermoelectric engines consist of two heat and particle reservoirs, which are permanently coupled by a conductor. Due to the Seebeck effect, the heat current flowing naturally in this setup can drive a particle current into the same direction thus generating electrical power. During the last decades, substantial efforts have been gone into the miniaturization of both of these types Thermoelectric heat engineof devices down to micro- and nanometers. On theses small scales, their operation principles can be scrutinized under the microscope by virtue of precise measurements of characteristic quantities like applied work or exchanged heat. Here, we use the framework of stochastic thermodynamics to investigate the laws that determine the efficiency and power of mesoscopic heat engines. In particular, we are interested in the relation between these two figures and the attainability of the Carnot efficiency, a universal upper bound following from the second law.

Related publications

Periodic thermodynamics of open quantum systems
K. Brandner and U. Seifert
Phys. Rev. E 93, 062134, 2016
Abstract Download (pdf icon pdf)

Optimal performance of periodically driven, stochastic heat engines under limited control
M. Bauer, K. Brandner, and U. Seifert
Phys. Rev. E 93, 042112, 2016
Abstract Download (pdf icon pdf)

Thermodynamics of micro- and nano-systems driven by periodic temperature variations
K. Brandner, K. Saito, and U. Seifert
Phys. Rev. X 5, 031019, 2015
Abstract Download (pdf icon pdf)

Bound on thermoelectric power in a magnetic field within linear response
K. Brandner and U. Seifert
Phys. Rev. E 91, 012121, 2015
Abstract Download (pdf icon pdf)

Classical Nernst engine
J. Stark, K. Brandner, K. Saito, and U. Seifert
Phys. Rev. Lett. 112, 140601, 2014
Abstract Download (pdf iconpdf)

Multi-terminal thermoelectric transport in a magnetic field: Bounds on Onsager coefficients and efficiency
K. Brandner and U. Seifert
New J. Phys. 15, 105003, 2013
Abstract Download (pdf iconpdf)

Strong bounds on Onsager coefficients and efficiency for three terminal thermoelectric transport in a magnetic field
K. Brandner, K. Saito, and U. Seifert
Phys. Rev. Lett., 110, 070603, 2013
Abstract Download (pdf iconpdf) Viewpoint

 


Stochastic (thermo-)dynamics of molecular motor-cargo systems

Molecular motor model

Molecular motors are enzymes that convert chemical energy from, e.g. ATP-hydrolysis into mechanical work. Operating in an aqueous solution, they exhibit stochastic dynamics and energetics due to the influence of thermal fluctuations. Experimental studies typically imply a probe particle that is attached to the motor and serves as a sensor to visualize the motor motion. Since these probe particles are much larger that the motor itself, they consitute a considerable hindrance that severely influences the dynamics and thermodynamics of the motor. This fact should be accounted for upon analyzing experimental data. We use a simple model taking into account explicitly the elastic coupling between the probe and the motor. The combined dynamics consists of discrete steps of the motor and the continuous Brownian motion of the probe. Motivated by recent experiments, we have applied this model to the F1-ATPase and have investigated three different types of efficiencies used to quantify the chemical to mechanical energy conversion. In a more general approach, the state of the motor can be considered as a generic hidden degree of freedom, whereas the probe particle represents a visible degree of freedom. The dynamics of the visible degree of freedom can be shown to obey a modified fluctuation relation. Moreover, we introduce a thermodynamically consistent method to map the detailed model onto a coarse grained model with a single effective motor particle.

Related publications

Effective rates from thermodynamically consistent coarse-graining of models for molecular motors with probe particles
E. Zimmermann and U. Seifert
Phys. Rev. E 91, 022709, 2015
Abstract Download (pdf icon pdf)

Fine-structured large deviations and the fluctuation theorem: Molecular motors and beyond
P. Pietzonka, E. Zimmermann, and U. Seifert
EPL 107, 20002, 2014
Abstract Download (pdf icon pdf)

Efficiencies of a molecular motor: A generic hybrid model applied to the F1-ATPase
E. Zimmermann and U. Seifert
New J. Phys. 14, 103023, 2012
Abstract Download (pdf iconpdf)

Efficiency of molecular motors at maximum power
T. Schmiedl and U. Seifert
EPL 83, 30005, 2008
Abstract Download (pdf iconpdf)

 


Thermodynamics and information

Szilard


The idea of using thermal fluctuations to extract useful work from a heat bath, thus creating an isothermal engine, is linked to the famous gedankenexperiments of Maxwell's demon (1867) and Szilard's engine (1929). In those experiments, a „demon“ extracts work cyclically from a heat bath by using the information acquired through the measurement of an adequate property - velocity or position - of the system. This apparent contradiction with the second law of thermodynamics was first resolved in 1967 by Rolf Landauer through his celebrated principle, which states that the erasure of a bit of information has a minimal energetic cost, thus linking thermodynamics to information theory. These concepts can nowadays be tested by experiments at the single-molecule level using the framework of stochastic thermodynamics. Our aim is to study theoretically systems for which one can convert information into work, e.g., by controlling the position of a Brownian particle in a laser trap.

peqxm1

The fact that one can indeed use such systems to extract work from a heat bath in finite-time has led us to the question of conceiving and simulating cyclic devices based on those principles. These devices use periodic measurements (feedback) to yield a positive power output, therefore working as motors. Moreover, we are interested in developing autonomous models for Maxwell's demon. With these models, we hope to shed light in issues that are not yet fully understood, as for example, the writing and erasure of information and the linear response theory.

Related publications

Stochastic thermodynamics of resetting
J. Fuchs, S. Goldt, and U. Seifert
EPL, 113, 60009, 2016
Abstract Download (pdf icon pdf)

Stochastic thermodynamics with information reservoirs
A. C. Barato and U. Seifert
Phys. Rev. E 90, 042150, 2014
Abstract Download (pdf icon pdf)

Unifying three perspectives on information processing in stochastic thermodynamics
A. C. Barato and U. Seifert
Phys. Rev. Lett. 112, 090601, 2014.
Abstract Download (pdf icon pdf)

Stochastic thermodynamics of bipartite systems: transfer entropy inequalities and a Maxwell's demon interpretation
D. Hartich, A. C. Barato, and U. Seifert
J. Stat. Mech., P02016, 2014
Abstract Download (pdf icon pdf)

Rate of mutual information between coarse-grained non-Markovian variables
A. C. Barato, D. Hartich, and U. Seifert
J. Stat. Phys. 153, 460-478, 2013
Abstract Download (pdf icon pdf)

An autonomous and reversible Maxwell's demon
A. C. Barato, U. Seifert
EPL, 101, 60001, 2013
Abstract Download (pdf icon pdf)

Efficiency of a Brownian information machine
M. Bauer, D. Abreu, and U. Seifert
J. Phys. A: Math. Theor. 45, 162001, 2012
Abstract Download (pdf iconpdf)

Thermodynamics of genuine non-equilibrium states under feedback control
D. Abreu and U. Seifert
Phys. Rev. Lett. 108, 030601, 2012
Abstract Download (pdf iconpdf)

Extracting work from a single heat bath through feedback
D. Abreu and U. Seifert
EPL 94, 10001, 2011
Abstract Download (pdf iconpdf)

 


Rate of mutual information in sensory networks

thermodAcquiring and processing information about the instantaneous state of the environment is a prerequisite for survival for any living system. Sensory and signal transducting networks have evolved to achieve this task under a variety of external conditions. Maintaining any biochemical network, however, has a metabolic cost associated with its inherent non-equilibrium nature. The rate of mutual information characterizes the rate with which they acquire information about the changing external conditions. Comparing this rate with the thermodynamic entropy production that quantifies the cost of maintaining the network, we find that there is no universal bound restricting the rate of obtaining information to be less than this thermodynamic cost. On the technical level, in order to obtain the rate of mutual information we calculate Shannon entropy rates of non-Markovian time-series.

Related publications

Information-theoretic vs. thermodynamic entropy production in autonomous sensory networks
A. C. Barato, D. Hartich, and U. Seifert
Phys. Rev. E 87, 042104, 2013
Abstract Download (pdf iconpdf)

 


Hidden degrees of freedom

Hidden degree of freedomMost physical descriptions involve some sort of coarse graining. Particulary in the description of meso or macroscopic systems one needs to deal with hidden fast degrees of freedom such as the myriads of solvent particles that are treated in an effective manner when describing the diffusion of a colloidal particle in the Langevin approach. Generally, an effective description of such unobserved degrees of freedom is justified if there is a clear-cut time-scale separation in the dynamics. Without such a time-scale separation, neglecting hidden slow degrees of freedom naively can lead to inconsistencies. Here, we investigate the role of hidden slow degrees of freedom in the fluctuation theorem for the apparent entropy production one would infer from a reduced set of variables.

Related publications

Role of hidden slow degrees of freedom in the fluctuation theorem
J. Mehl, B. Lander, C. Bechinger, V. Blickle, and U. Seifert
Phys. Rev. Lett. 108, 220601, 2012
Abstract Download (pdf iconpdf)

Can one identify non-equilibrium in a three state system by analyzing two-state trajectories?
C. Amann, T. Schmiedl, and U. Seifert
J. Chem. Phys. 132, 041102, 2010
Abstract Download (pdf iconpdf)

 


Efficiency of nanomachines

BildMolecular motors as well as the recently developed artificial nanomachines inspired by them operate in an aqueous solution of constant temperature. In contrast with heat engines limited by Carnot’s law, thermodynamics constrains their efficiency by 1. Like for heat engines, however, operating at the upper bound comes at the price of zero power since it requires infinitely slow driving. A practically more relevant question then is about efficiency at maximum power which we have analyzed for autonomous soft nanomachines using a quite general approach requiring minimal assumptions.

Related publications

Efficiency of autonomous soft nano-machines at maximum power
U. Seifert
Phys. Rev. Lett. 106, 020601, 2011
Abstract Download (pdf iconpdf)

Stochastic thermodynamics of single enzymes and molecular motors
U. Seifert
Eur. Phys. J. E 34, 26, 2011
Abstract Download (pdf iconpdf)

Efficiency at maximum power: An analytically solvable model for stochastic heat engines
T. Schmiedl and U. Seifert
EPL 81, 20003, 2008
Abstract Download (pdf iconpdf) Experimental realization

 


Fluctuation-dissipation theorem and Green-Kubo relations for non-equilibrium steady states

Nonequilibrium steady states (NESSs) are characterized both by a time-independent distribution and, as a result of the external driving, nonvanishing currents. If such a NESS is perturbed by an additional small external force or field, one can ask whether the response of an observable of this system can be expressed by a correlation function similarly to the well-known equilibrium fluctuation-dissipation theorem (FDT). By expressing entropy production in the system as the difference between total entropy production and that in the surrounding medium, we can show that for a large class of systems the FDT in a NESS can be obtained from the corresponding equilibrium form of the FDT by subtracting a term involving total entropy production. Similarly, we have derived generalized Green-Kubo relations for such NESSs that relate transport coefficients and fluctuations around a stationary mean current.

Related publications

Generalized Einstein or Green-Kubo relations for active biomolecular transport
U. Seifert
Phys. Rev. Lett. 104, 138101, 2010
Abstract Download (pdf iconpdf)

Fluctuation-dissipation theorem in nonequilibrium steady states
U. Seifert and T. Speck
EPL 89, 10007, 2010
Abstract Download (pdf iconpdf)

 


Approximate thermodynamic structure for driven lattice gases

 

ToriInKontaktMitE6_fig1

 

In this project, we are studying the particle exchange between driven systems. Our model describes two driven lattice gases which may exchange particles through a small contact area with the total number of particles conserved. Checking a putative zeroth law and the corresponding fluctuation-response relation regarding particle number in simulation, we want to clarify, if it is possible to characterize a homogenously driven many-particle system in terms of an intensive variable, like the chemical potential.

Related publications

Thermodynamic theory of phase transitions in driven lattice gases
P. Pradhan and U. Seifert
Phys. Rev. E 84, 051130, 2011
Abstract Download (pdf iconpdf)

Approximate thermodynamic structure for driven lattice gases in contact
P. Pradhan, R. Ramsperger, and U. Seifert
Phys. Rev. E 84, 041104, 2011
Abstract Download (pdf iconpdf)

Nonequilibrium steady states in contact: Approximate thermodynamic structure and zero-th law for driven lattice gases
P. Pradhan, C. Amann, and U. Seifert
Phys. Rev. Lett. 105, 150601, 2010
Abstract Download (pdf iconpdf)

 

 


[top][Membrane adhesion] [Soft matter in flow]