Publikation: Interplay between charging effects and multiparticle charge transport processes in a tunable single electron transistor
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In this thesis we study a device called single electron transistor (SET) where one of the junctions is a tunable atomic contact. Our device consists of an oxide tunnel barrier in series with a mechanically controlled break junction (MCBJ), being the element that allows to adjust the atomic contact. With this technique, it is possible to tune the electronic transmission of the atomic contact and thereby the coupling strength between the island and the re- spective electrodes. The part between both barriers is the island, and the energy for transferring an electron into it is the charging energy. Lowering thermal fluctuations, by cooling down the device to temperatures below 1K, and quantum fluctuations, by utilising junctions with a very small capaci- tance, make the charging energy (EC) the characteristic energy of the SET. A third electrode is coupled to the island to act as a gate.
Until the applied energy exceeds EC transport through the SET is not possible. This is known as Coulomb blockade (CB), and gives rise to the CB oscillations and diamonds. We will explore the limits for the CB signatures depending on the coupling of the atomic contact to the island. We will be able to characterise how charging effects vanish for higher transmission of the atomic contact, and also, how CB and the well defined charge states inside the island vanish.
Using a superconducting material for one (or several) parts of the SET allows to have more types of transport, and in particular, multi-charge trans- port, namely Cooper pair transport and (multiple) Andreev reflections. In our devices, the island and one of the leads are made out of a superconduc- tor (aluminium) and connected by a MCBJ. The other lead is made out of a normal material (copper) and is coupled to the island via an oxide bar- rier. This device bridges between the widely studied and better understood NSN-SET and the SSS-SET, which has a very high amount of possible trans- port processes and that has made it so far challenging to disentangle these processes.
Therefore, in the second part of the thesis, we will present how the charg- ing effects interfere with the multi-particle transport in the MCBJ. We will study how EC modulates the different Cooper pairs and Andreev reflections over the MCBJ, and we will also be able to present such data for the strong- coupling regime. Having an atomic contact as one of the barriers in the SET allows to tune these multi-particles processes by adjusting the coupling of one electrode to the island. Charging effects caused by CB disappear when bringing the atomic contact to very large transmission.
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SOBRAL REY, Laura, 2024. Interplay between charging effects and multiparticle charge transport processes in a tunable single electron transistor [Dissertation]. Konstanz: Universität KonstanzBibTex
@phdthesis{SobralRey2024-10-01Inter-70985, year={2024}, title={Interplay between charging effects and multiparticle charge transport processes in a tunable single electron transistor}, author={Sobral Rey, Laura}, address={Konstanz}, school={Universität Konstanz} }
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