Masters Defense: Davydas Razmadze – University of Copenhagen

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Center for Quantum Devices > QDev Calendar > 2017 > Masters Defense: Davyd...

Masters Defense: Davydas Razmadze

Thesis title: "Charge sensing of epi-Al InAs nanowire devices"
Subtitle: "Towards Majorana Fusion rule experiment"


"Majorana fermions in condensed matter systems have attracted a lot of attention since first strong signatures came from Mourik et al. of Majorana bound states in proximitized nanowires. Other groups quickly followed identifying and reproducing the same results and pushing forward to understand the dynamics of Majorana bound states in 1D systems. The main interest in these quasiparticles that they exhibit non-Abelian exchange statistics and can be encoded as a topologically protected qubits.

My main focus of the thesis, was to develop a nanowire based system, where charge readout can be done on Majorana fusion rule experiment devices. With a successful device material and geometry combination, such devices were fabricated and investigated at low temperatures. The devices that were measured are first of their kind, were charge sensing of each and individual nanowire superconducting islands is possible. The devices have the ability to be tuned from single to double quantum dots and vice versa, while taking charge sensing data. Even/odd effect at finite magnetic fields was also observed, indicating that epitaxially grown Al, fully proximitized the semiconductor. Majorana search in these devices was also conducted and presented in this thesis, with a zero bias conductance peak observed at o 275 mT. Conclusions are given according to individual achievement that were done in this thesis. Although, these devices ar still not the ultimate Majorana fusion rule experiment devices, an
outlook for new and modified devices are presented as well."