Investigating TLS loss contributions in superconducting microwave resonators at millikelvin temperatures

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School of Science | S harjoitus- ja seminaarityöt
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2023

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Teknillisen fysiikan laitos
Department of Applied Physics

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en

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34

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Abstract

Geometrically identical superconducting microwave resonators (SMR) fabricated on bare silicone and aluminum oxide substrates are characterized and compared in terms of internal quality factor and resonance frequency shift. The presented data covers a wide temperature and power range of 400 mK and six orders of magnitude, respectively. The quality of resonators on bare Si is clearly found to be one order magnitude higher than in the presence of an aluminum oxide layer. A numerical analysis and fits to an established model for two-level-systems (TLS) loss strongly support this finding. However, the model fails to adequately describe the consistently showing characteristic back-bending behavior of the temperature dependent total loss tangent below 100 mK. Only sparsely reported in literature, this feature and its mathematical description raise significant doubts about the applicability of established TLS models in this low-temperature regime. A thorough literature research introduces modifications and extensions to the established model proposed in recent publications.

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superconducting 2D resonators, two-level-systems, coplanar waveguides, nanofabrication

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https://urn.fi/URN:NBN:fi:aalto-202502142432

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[sem] Perustieteiden korkeakoulu / SCI