Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 50: Superconducting Electronics: SQUIDs, Qubits, Circuit QED II

TT 50.4: Vortrag

Donnerstag, 20. März 2025, 15:45–16:00, H36

Two-level system involved nonlinear response in van der Waals hybrid microwave resonators — •Haolin Jin^1,3, Giuseppe Serpico^1,2, Yejin Lee¹, Berit Goodge¹, Edouard Lesne¹, Nicola Poccia^2,3, and Uri Vool¹ — ¹Max Planck Institute for Chemical Physics of Solids, Dresden, Germany — ²University of Naples Federico II, Italy — ³Leibniz Institute for Solid State and Materials Science Dresden, Germany

Two-level system (TLS) bath is considered as the main loss channel in coplanar superconducting microwave resonators and is often associated with an upshift in resonance frequency as the temperature increases. The individual TLS can be saturated at the high input power, improving the quality factor of the resonator. However, the resonance frequency upshift remains unaffected by driving power because all TLS at different energy can contribute to the frequency shift, whereas only those close to the resonance frequency can be saturated. Here, we observed a positive nonlinearity in a van der Waals superconductor integrated hybrid resonator device. The hybrid device exhibited a significant upshift in resonance frequency with increasing temperature, indicating strong coupling to a TLS bath. It maintained a high-quality factor despite this coupling. These findings suggest that the resonance mode in the hybrid device is coupled to an off-resonant TLS bath and the hybrid system provides a new source of lossless nonlinearity unrelated to the Josephson effect. This work opens a path towards high quality hybrid superconducting circuits with vdW materials and highlights the development of new devices for quantum technology.

Keywords: Two-level system; nonlinearity; Superconducting van der Waals materials; Superconducting microwave circuits