Most efficient quantum thermoelectric at finite power output

Area of Science:

• Quantum thermodynamics
• Condensed matter physics
• Nanoscale energy conversion

Background:

• Carnot efficiency sets the theoretical limit for heat engines but requires reversible processes with zero power output.
• Irreversible devices offer finite power but operate below Carnot efficiency.
• Thermoelectric quantum systems, such as nanostructures and molecules, exhibit the Peltier effect, enabling heat-to-electricity conversion.

Purpose of the Study:

• To determine the maximum achievable efficiency for irreversible quantum thermoelectric devices operating at finite power output.
• To investigate the influence of quantum mechanics on the efficiency limits of nanoscale heat engines and refrigerators.

Main Methods:

• Application of nonlinear scattering theory to analyze quantum thermoelectric systems.
• Investigation of quantum systems exhibiting the Peltier effect, including nanostructures and molecules.

Main Results:

• Quantum mechanics imposes fundamental upper bounds on both power output and efficiency for irreversible devices.
• The maximum efficiency, bounded by quantum mechanics, equals Carnot efficiency only at zero power output and decreases as power output increases.
• This quantum efficiency limit is wavelength-dependent, distinguishing it from the universal Carnot efficiency.

Conclusions:

• A quantum-mechanical upper bound on efficiency exists for irreversible thermoelectric devices at finite power.
• The maximum efficiency is achieved when the system selectively transmits particles within a specific energy window.
• Phonon heat flow can suppress the efficiency of these quantum devices, highlighting practical limitations.