Condensed Matter Physics Seminar: Sofia Sevitz

Abstract: Fermionic devices—like quantum dots that spatially confine electrons—bring quantum effects like the Pauli exclusion principle and parity anti-symmetrization front and centre, making them prime candidates for groundbreaking quantum technologies. My talk will take a step further and dive into nanoelectromechanical systems (NEMS), where electronic transport through a quantum dot is intrinsically coupled to mechanical motion of an oscillator. This simple system covers a wide range of platforms ranging from carbon nanotubes with an embedded quantum dot to molecular junctions, showcasing a versatile playground for research developments, specifically for thermodynamics in the quantum realm.

The presentation will be structured in three parts.

In the first part, I will introduce a newly derived quantum master equation describing NEMS dynamics in the regime where electronic transport is slower than the oscillator’s natural frequency [1]. This regime necessitates a fully quantum treatment, surpassing semiclassical models. Our approach also incorporates energy-dependent tunnelling rates, extending beyond the wideband limit to more faithfully represent realistic device behaviour. Benchmarking against numerically exact solutions reveals excellent agreement in the non-equilibrium steady state. Moreover, we derive expressions for the particle current that align closely with previous experimental observations.

Building on this framework, the second part will explore a key application: an autonomous converter of particle-exchange to quantum self-oscillations [2]. Here, the focus is on understanding how particle-exchange machines interact with quantum work-like mechanical loads, which allow for power output to be stored in internal degrees of freedom.  With this, we hope to encourage the community to study work extraction and storage using this and similar platforms that couple to quantum-mechanical work loads.

In the final part, I will discuss ongoing work studying work extraction from the mechanical oscillator—acting as a quantum battery—powered by energy flow from a non-equilibrium charger. This charger consists of a quantum dot coupled to two reservoirs maintained at different temperatures and/or chemical potentials.

Although the work in this talk is fully theoretical, the framework developed here can be readily implemented in a variety of experimental nanoscale devices.

[1] S. Sevitz, F. Cerisola, and J. Anders, Quantum master equation of nanoelectromechanical systems beyond the wide-band limit, arXiv:2506.20593 (2025)
[2]  S. Sevitz, F. Cerisola, K. Hovhannisyan, and J. Anders, Autonomous conversion of particle-exchange to quantum self-oscillations, arXiv:2508.16206 (2025)