Models of heat machines have been historically used to study basic thermodynamic questions and establish its fundamental laws. The Carnot engine is a prime example of this approach.
That is the reason why so many groups have used models of quantum heat machines to study thermodynamic questions at the quantum level.
Several studies on quantum thermodynamics gave rise to a basic question: could a heat machine governed by quantum mechanics preform differently than its classical counterpart? The answer is yes, as shown by our group.
Classically, a volume change is required in order to extract or inject mechanical work (for a gas or liquid W = pdV).
In contrast, quantum heat machines can operate using an incompressible fluid that undergoes transformations that change the shape of the “combustion chamber” but not the volume. This effect relies on the fact that boundary effects can be neglected for macroscopic classical systems and their thermodynamic behavior mainly depends on the bulk of the system (the volume) and not the shape (related to the boundary). In contrast, for quantum systems the energy levels are highly sensitive to boundary conditions. What other properties are exclusive to quantum heat machines?
Another interesting effect we found is related to the stability of molecular junctions that we studied using the perspective of quantum heat engines. Molecular junctions are single molecules bonded to electrodes that transmit charge between them. We have found what seems like a counterintuitive effect. We can cool down (equivalent to stabilize) the molecule by increasing the temperature of the electrodes. This effect is known as cooling by heating and we are currently investigating its properties.
Our group continues to study quantum heat machines to better understand the role of thermodynamics on quantum systems.
Single-atom heat machines enabled by energy quantization:
Quantum features and signatures of quantum thermal machines:
Cooling by Heating:
A Great Overview About Quantum Thermodynamics