Magnetic field dependent microwave losses in superconducting niobium microstrip resonators

Abstract

We describe an experimental protocol to characterize magnetic field dependent microwave losses in superconducting niobium microstrip resonators. Our approach provides a unified view that covers two well-known magnetic field dependent loss mechanisms: quasiparticle generation and vortex motion. We find that quasiparticle generation is the dominant loss mechanism for parallel magnetic fields. For perpendicular fields, the dominant loss mechanism is vortex motion or switches from quasiparticle generation to vortex motion, depending on cooling procedures. In particular, we introduce a plot of the quality factor versus the resonance frequency as a general method for identifying the dominant loss mechanism. We calculate the expected resonance frequency and the quality factor as a function of the magnetic field by modeling the complex resistivity. Key parameters characterizing microwave loss are estimated from comparisons of the observed and expected resonator properties. Based on these key parameters, we find a niobium resonator whose thickness is similar to its penetration depth is the best choice for X-band electron spin resonance applications. Finally, we detect partial release of the Meissner current at the vortex penetration field, suggesting that the interaction between vortices and the Meissner current near the edges is essential to understand the magnetic field dependence of the resonator properties.

Magnetic-Field-Resilient Superconducting Coplanar-Waveguide Resonators for Hybrid Circuit Quantum Electrodynamics Experiments

“…In order to create high Q i SC resonators that can survive in strong magnetic fields, controlling the creation and dynamics of Abrikosov vortices is key. Previous studies have utilized the intrinsic disorder in NbTiN [40] and YBCO [41] films, or litho-arXiv:1809.03932v1 [cond-mat.mes-hall] 11 Sep 2018 graphically defined artificial defect sites [42] to pin the vortices, preventing dissipation and demonstrating moderate quality factors up to 10 4 in parallel magnetic fields. In other studies, the resonator geometry has been restricted below the superconducting penetration depth to prevent the formation of vortices entirely [43][44][45][46].…”

Superconductivity and Microwaves

“…The electrodynamics theory of E and B fields and losses, Q , in resonant cavities is well developed. Jackson [31], Csősz et al [55], Kwon et al [56], and other books [1,2] have explicit equations for losses due to dielectric, metallic, or superconducting materials. Following Kwon et al, here we present in compact form (block diagram) ( Figure 11A) a summary of the electrodynamics and losses of superconductors in resonant cavities.…”

“…As a manner of example, we take the case of magnetic field dependent microwave losses in superconducting niobium microstrip resonators reported by Kwon et al [56]. They find that quasiparticle generation is the dominant loss mechanism for parallel magnetic fields.…”

Engineering nonlinear response of superconducting niobium microstrip resonators via aluminum cladding

“…To calculate the expected f and Q as a function of H , we need to model the complex resistivity 35 .…”

“…For further details about the growth conditions, see Ref 30. and the supplementary material of Ref 35,. in which the films for Al-0H and Al-0L are appeared as wafers A and C, respectively.…”