IFIBA   22255
INSTITUTO DE FISICA DE BUENOS AIRES
Unidad Ejecutora - UE
artículos
Título:
Vibrational cooling and thermoelectric response of nanoelectromechanical systems
Autor/es:
ARRACHEA, L.; BODE, NIELS; VON OPPEN, FELIX
Revista:
PHYSICAL REVIEW B
Editorial:
AMER PHYSICAL SOC
Referencias:
Lugar: New York; Año: 2014 vol. 90 p. 125450 - 125451
ISSN:
1098-0121
Resumen:
An important goal in nanoelectromechanics is to cool the vibrational
motion, ideally to its quantum ground state. Cooling by an applied
charge current is a particularly simple and hence attractive strategy to
this effect. Here we explore this phenomenon in the context of the
general theory of thermoelectrics. In linear response, this theory
describes thermoelectric refrigerators in terms of their cooling
efficiency eta and figure of merit ZT. We show that both concepts
carry over to phonon cooling in nanoelectromechanical systems. As an
important consequence, this allows us to discuss the efficiency of
phonon refrigerators in relation to the fundamental Carnot efficiency.
We illustrate these general concepts by thoroughly investigating a
simple double-quantum-dot model with the dual advantage of being quite
realistic experimentally and amenable to a largely analytical analysis
theoretically. Specifically, we obtain results for the efficiency, the
figure of merit, and the effective temperature of the vibrational motion
in two regimes. In the quantum regime in which the vibrational motion is
fast compared to the electronic degrees of freedom, we can describe the
electronic and phononic dynamics of the model in terms of master
equations. In the complementary classical regime of slow vibrational
motion, the dynamics is described in terms of an appropriate Langevin
equation. Remarkably, we find that the efficiency can approach the
maximal Carnot value in the quantum regime, with large associated
figures of merit. In contrast, the efficiencies are typically far from
the Carnot limit in the classical regime. Our theoretical results should
provide guidance to implementing efficient vibrational cooling of
nanoelectromechanical systems in the laboratory.