Speaker
Description
Energy conversion processes in nanoscale devices are potentially strongly impacted by fluctuations. It is therefore of high interest to understand if and how these fluctuations are related to the desired outcome of the process. While in systems close to equilibrium, fluctuation-dissipation theorems exist, relating the fluctuations to the average response of the system, such relations are typically harder to find in nonequilibrium situations. More general fluctuation relations, holding also in nonequilibrium, are at the basis of recently studied bounds on the fluctuations such as the so-called thermodynamic uncertainty relation. These are however typically applicable mostly to classical or weakly coupled systems.
In this talk I will present recent progress in establishing constraints on the fluctuations in nonequilibrium, possibly strongly coupled systems. These results are obtained from scattering theory, which applies to a large class of systems, as long as particle-particle interactions are weak. For nanoscale heat engines, possible subject to a large temperature bias, we find a bound on the power fluctuations given by the power itself, which holds even when the thermodynamic uncertainty relation breaks down [1]. Furthermore, we prove a sort of kinetic uncertainty relation for quantum transport of particles, energy or entropy, which in the classical limit bounds the precision by the “activity” of the system - independently of whether the system is bosonic or fermionic and even when the contacts are nonthermal [2]. In the quantum regimes, these kinetic uncertainty relations need to be modified, where the quantum statistics (fermionic/bosonic) play an important role for the validity and shape of these bounds.
[1] L. Tesser, J. Splettstoesser: Out-of-Equilibrium Fluctuation-Dissipation Bounds. Phys. Rev. Lett. 132, 186304 (2024)
[2] D. Palmqvist, L. Tesser, J. Splettstoesser: Quantum kinetic uncertainty relations, in preparation.
