PhD Thesis: Electrically and thermally driven transport in interacting quantum dot structures

May 28, 2019

We are proud to congratulate Miguel A. Sierra on the successful defense of his thesis work, "Electrically and thermally driven transport in interacting quantum dot structures", supervised by David Sánchez.

His thesis, defended on Thursday 11th April, deals with one of the most innovative examples of nanodevices: the so-called quantum dots, a system of electrons trapped in every dimension of space due to electrostatic confinement. An advantage of these devices is that their quantum states can be controlled by applying voltages. For this reason, quantum dots are the ideal candidates to perform as qubits, the quantum analogue of the classical bit, which are essentials for the fabrication of quantum computers.

Sierra’s PhD thesis studies quantum dot systems in which electron-electron interactions take an important role to the electric and thermoelectric transport, where currents are induced by electric potentials or thermal differences, respectively. These devices display Coulomb blockade and Kondo effect, which appears at strong electronic interactions and low temperatures. 

In this thesis, it is found that the thermoelectric transport can be significantly different from the electric one in which transport can even vanish at certain thermal biases. The reason of this behavior is that there exist more than one transport channel generating electron flows in different directions. 

Regarding serially-coupled quantum dots, that mimic an artificial molecule the thesis investigates the competition between the Kondo effect and the dot-dot antiferromagnetic interaction in the presence of a thermal gradient.  On the other hand, in parallel-coupled quantum dots, interference phenomena emerge and bound states in the continuum are created. 

Finally, the Coulomb drag in interacting parallel double quantum dots has also been analyzed. Here, the transport through one of the quantum dot induces charge fluctuations that affects the transport of the other quantum dot. 

In summary this thesis work is relevant in view of finding efficient machines able to partially recover the waste heat into electric current and allows a better understanding of the transport through quantum dots in order to improve the characterization and fabrication of these nanodevices. 

Sierras’s PhD dissertation was presented to the members of the jury Antti-Pekka Jauho (Technical University of Denmark), Leonid Glazman (University of Yale) and Gloria Platero (Instituto de Ciencia de Materiales de Madrid), who qualified the thesis defense with the highest mark (excellent cum laude). 

Photo: A. Costa (UIB)

 Miguel A. Sierra

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