Heat capacities of thermally manipulated mechanical oscillator at strong coupling

Abstract

Coherent quantum oscillators are basic physical systems both in quantum statistical physics and quantum thermodynamics. Their realizations in lab often involve solid-state devices sensitive to changes in ambient temperature. We represent states of the solid-state optomechanical oscillator with temperature-dependent frequency by equivalent states of the mechanical oscillator with temperature-dependent energy levels. We interpret the temperature dependence as a consequence of strong coupling between the oscillator and the heat bath. We explore parameter regimes corresponding to anomalous behavior of mechanical and thermodynamic characteristics as a consequence of the strong coupling: (i) The localization and the purification induced by heating, and (ii) the negativity of two generalized heat capacities. The capacities can be used to witness non-linearity in the temperature dependency of the energy levels. Our phenomenological experimentally-oriented approach can stimulate development of new optomechanical and thermomechanical experiments exploring basic concepts of strong coupling thermodynamics.

Strong Coupling and Nonextensive Thermodynamics

“…However, for systems with sufficiently low energy or sufficiently strong interactions, the system’s energy is comparable to the interaction energy, and the latter may no longer be neglected. Indeed, the presence of the interaction causes the effective Hamiltonian to be temperature-dependent, as long suggested by Elcock and Landsberg [ 16 ] and others [ 15 , 17 , 18 , 19 , 20 ].…”

Internal Geometric Friction in a Kitaev Chain Heat Engine

“…The method of TDELs has been proposed as a fast and convenient way to perform statistical mechanical calculations for an assembly of systems [17,18]. It has been applied to semiconductors [29][30][31][32], superfluids [33], optomechanical oscillators [34,35], heat losses in thermoelectric systems [22,23], and thermalization of finitesize systems [19][20][21]. TDELs can be associated with a temperature-dependent effective Hamiltonian, or a so called "Hamiltonian of mean force" arising as the result of a prior averaging over certain possible microstates of the assembly in thermal equilibrium [36,37].…”

High-precision multiparameter estimation of mechanical force by quantum optomechanics

“…We will consider a small force that can both displace and squeeze mechanical motion in position and momentum variables. Mechanical displacement and squeezing not only provide information about nanomechanical processes, they have also become important resources in the field of quantum thermodynamics 11 – 14 . To reliably recognize their presence and potential, all aspects of a weak force F ( q ) linearized around any position have to be simultaneously estimated.…”