Open Quantum Systems

Non-equilibrium devices such as thermoelectric devices, solar cells, and heat machines exploit energy/particle currents that flow through a system coupled to multiple baths.

Although the fluxes increase as the coupling strengthens in the weak coupling regime, why they decrease to zero for large coupling values remains unknown.

This turnover effect has been predicted in several systems such as photosynthetic complexes, thermoelectric devices and chemical networks, without a single counterexample, resulting in a constrained performance due to the limited currents.

We also found that this effect limits the performance of heat machines.

The ubiquity of this effect could indicate its universality and a fundamental physical mechanism behind it.

In our group, we are studying the “turnover effect” and unveiling the physical mechanism behind it.

For this, we use both numerical and analytical methods to analyze the “turnover effect” and look for common physical behaviors among widely different realizations.

Moreover, we are looking for basic design principles that will help avoid or minimize the impact of the turnover effect on microscopic non-equilibrium devices, such as nano-heat machines or thermoelectric devices, and unleash the full potential of these devices.

These are

Some of the questions we are exploring:

Is the turnover effect a universal behavior and what are its characteristics?

What are the physical mechanisms behind the turnover effect?

How could we prevent the turnover effect?


Some of our papers:

The “Turnover Effect” In Heat Engines

Strongly Coupled Quantum Heat Machines

Gelbwaser-Klimovsky, D. & Aspuru-Guzik, A. J. Phys. Chem. Lett. 6, 3477–3482 (2015)


Other Group's Papers:

The “Turnover Effect” In Chemical Reactions

Rips, I. & Pollak, E. Quantum Kramers model: Solution of the turnover problem. Physical Review A 41 (1990):5366.

The “Turnover Effect” In the Spin-Boson model

Wang, C., Ren, J. & Cao, J. Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling. Sci Rep 5 (2015):11787

The “Turnover Effect” for Spin baths

Katz, G. & Kosloff, R. Quantum Thermodynamics in Strong Coupling: Heat Transport and Refrigeration. Entropy 18, (2016):186