Geometric properties of adiabatic thermal machines

Speaker: Liliana Arrachea, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires

When: December 2, 2020 (Wed), 01:00PM to 02:00PM (add to my calendar)

This event is part of the Biophysics/Condensed Matter Seminar Series.

Starting from the seminal works of Aharonov and Bohm and Berry, geometric effects have pervaded many areas of physics. In quantum transport, distinct contributions of geometric origin affect charge and energy currents. In the absence of an additional dc bias, the pumped charge in a periodically driven system was shown to be of geometric origin, and can thus be expressed in terms of a closed-path integral in parameter space, akin to the Berry phase. Geometric concepts like a thermodynamic metric and a thermodynamic length were recently introduced as promising tools to characterize the dissipated energy and to design optimal driving protocols. Similar ideas are behind the description of the adiabatic time-evolution of many-body ground states of closed systems in terms of a geometric tensor. This large body of work linking geometry to transport naturally hints at similar connections for thermal machines. In this seminar, I will discuss how, under quite general assumptions, the operation of quantum thermal machines and the underlying heat-work conversion is fundamentally tied to such geometric effects. We recently formulated a unified description in terms of a geometric tensor for all the relevant energy fluxes, which we refer to as thermal geometric tensor [1]. Within this description, pumping and dissipation are, respectively, associated with the antisymmetric and symmetric components of this tensor. Simple examples of the operation are a slowly driven qubit asymmetrically coupled to two bosonic reservoirs kept at different temperatures, and a quantum dot driven by a rotating magnetic field and strongly coupled to electron reservoirs with different polarizations. [1]Geometric properties of adiabatic quantum thermal machines (https://journals.aps.org/prb/abstract/10.1103/PhysRevB.102.155407, arXiv:2002.02225) Bibek Bhandari, Pablo Terrén Alonso, Fabio Taddei, Felix von Oppen, Rosario Fazio, Liliana Arrachea