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PhD Defense: Transport and thermodynamics in driven quantum systems

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Speaker: Patrick Haughian
Event date: Thursday, 18 October 2018 02:00 pm - 03:00 pm
Place: Limpertsberg Campus, Room BS 0.03

PhD Supervisor: A.-Prof. Thomas Schmidt

The properties of quantum dots are studied with regard to electrical conduction as well as thermodynamics. The work presented here shows how these properties behave under the influence of time-dependent drive protocols, pursuing two main lines of inquiry. The first concerns the interplay between nanomechanics and drive: In nanomechanical systems with strong coupling between the charge and vibrational sectors, conductance is strongly suppressed, an effect known as Franck-Condon blockade. Using a model Hamiltonian for a molecular quantum dot coupled to a pair of leads, it is shown here that this blockade can be exponentially lifted by resonantly driving the dot. Moreover, a multi-drive protocol is proposed to facilitate charge pumping that enjoys the same exponential amplification. The second line of inquiry examines the thermodynamics of a driven quantum dot coupled to a lead. Taking a Green's function approach, it is found that the laws of thermodynamics can be formulated for arbitrary dot-lead coupling strength in the presence of dot and coupling drive, as long as the drive protocol is quasi-adiabatic. Finally, the effects of initial states are studied, proving that the integrated work production in the long-time limit conforms to the second law of thermodynamics for a wide class of initial states and arbitrary drive and coupling strength.