Quantum Thermodynamics
and Full Counting Statistics
Thermodynamics of systems at nanoscale is at the heart of understanding and controlling the processes in the world of small systems from cells in biology to memory chips and optoelectric nano-devices in molecular electronics. Indeed, establishing a thermodynamically consistent description for open quantum system is of crucial importance for mesoscopic physics and for the study of energy conversion in small devices. Small size and open character of such devices implies importance of quantum and stochastic effects.Stochastic character of processes in open systems requires probabilistic description, which is intimately related to the full counting statistics (FCS). These issues have direct implications on defining meaningful notions of efficiency in thermoelectricity or photoelectricity.
While thermoelectric research in bulk materials goes back to the middle of the last century, measurements at nanoscale (and in particular, studies of thermoelectricity in molecular junctions) were reported only recently. Small size of the devices implies importance of stochasticity and quantum effects. Within the NEGF technique we derive the FCS of heat and work, and apply it to description of the efficiency fluctuation in such devices. We argue that for molecular junctions the nonequilibrium efficiency fluctuation is the appropriate characteristic to be used instead of often employed figure of merit.
With the development of experimental techniques measurements beyond the current-voltage became possible also in molecular junctions. This resulted in a theoretical challenge to extend the FCS formulation to describe inelastic effects. Very often electron-vibration interaction are treated within the Born approximation (BA). The BA is known to be a non-conserving approximation, and it may lead to unphysical predictions. The self-consistent BA (SCBA) is the proper alternative used in the standard NEGF studies with electron-vibration interaction treated within perturbation theory. We considered the NEGF-FCS formulation for the inelastic transport employing the SCBA. Our consideration is a first self-consistent formulation of the FCS. The approach is directly applicable to realistic simulations of inelastic transport in molecular junctions.
Representative publications:
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K.Miwa, F. Chen, and M. Galperin. Towards Noise Simulation in Interacting Nonequilibrium Systems Strongly
Coupled to Baths. Sci. Rep. 7, 9735 (2017).
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M.Esposito, M. A. Ochoa, and M. Galperin. Efficiency Fluctuations in Quantum Thermoelectric Devices. Phys. Rev. B 91, 115417 (2015).
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M.Esposito, M. A. Ochoa, and M. Galperin. Quantum Thermodynamics: A nonequilibrium Green’s function
approach. Phys. Rev. Lett. 114, 080602 (2015). Editors’ Suggestion
T.-H. Park and M. Galperin. Self-Consistent Full Counting Statistics in Inelastic Transport.
Phys. Rev. B 84, 205450 (2011).
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J.Fransson and M. Galperin. Spin Seebeck Coefficient of a Molecular Spin Pump. Phys. Chem. Chem. Phys. 13, 14350-14357 (2011).
