Wednesday 4 October 2023, 3:00pm to 4:00pm
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Condensed Matter Physics Seminar Tuneable impedance environment for quantum phase slip experiments By Jorden Senior
Condensed Matter Physics Seminar
Tuneable impedance environment for quantum phase slip experiments
By Jorden Senior
Start Time: Wednesday 04/10/2023 15:00
Tunnelling of magnetic vortices through a thin superconducting nanowire, i.e. quantum phase slips (QPS), can cause an insulating transition instead of the typical zero resistance state. This phenomenon is dual to Cooper pair tunnelling in a Josephson junction with quantum conjugate variables phase and charge exchanged. Thus, in analogy with the Josephson voltage standard yielding an ultra-precise frequency-to-voltage conversion , the QPS nanowire may allow a very precise quantum current standard. However, even though the experimental realization of coherent QPS was reported , and weak reverse Shapiro effect-like features in superconducting nanowires observed in [3,4], robust observations have been elusive, and only recently started to materialize [5,6].
We have developed a mK-temperature-operational FET platform  to be used as an integrated tuneable impedance environment for ultra-thin TiN and NbN superconducting nanowires. Our goal is to provide experimental data and theoretical models for the fundamental understanding of the QPS effect and to study the impact of geometric and material inhomogeneity, charge disorder and noise .
Recently, we have begun validation of the platform by embedding a Josephson junction in the tuneable environment, observing the evolution of the Coulomb blockade across the junction by gate-tuning the environment across the resistance quantum threshold.
Additionally, I will present recent experiments  on a wafer-scale method for amorphising superconducting thin films using either argon or gallium ion irradiation on single-element and compound materials where our results indicate that both ions increase disorder in the atomic structure in a qualitatively similar manner, i.e., they destroy the grain structure, increase resistivity and alter the superconducting transition temperature.
Finally, I will give a brief overview of related research activities at VTT relevant to superconducting quantum hardware and sensing applications.
 A. K. Jain et al, PRL 58, 1165 (1987)
 O. V. Astafiev et al., Nature 484, 355–358 (2012)
 J. S. Lehtinen et. al, Phys. Rev. Lett. 109, 187001 (2012)
 Z. M. Wang et al., App. Phys. Lett., 114, 242601 (2019)
 R. S. Shaikhaidarov et al. Nature 608, 45–49 (2022)
 N. Crescini et al, Nature Physics (2023)
 J. Duan et al., Appl. Phys. Lett. 118, 164002 (2021)
 S. E. de Graaf, Phys. Rev. B 102, 144509, (2020)
 K. Kohopää et al, arXiv:2303.11202 (2023)