Microwave Studies of Single Crystal TeO2 at Cryogenic Temperatures

Abstract

We use whispering-gallery-mode analysis to characterise the microwave dielectric properties of single-crystal TeO${}_2$ at cryogenic temperatures and compare its loss performance with other low-loss dielectric materials. Finite-element modelling is combined with measurements at room temperature, 4 K, and 20 mK to develop accurate cryogenic simulations and extract the anisotropic dielectric permittivities, giving ${\epsilon }_{\parallel }=25.75\pm 0.08$ and ${\epsilon }_{\perp }=20.90\pm 0.07$. Loss measurements reveal quality factors as high as $9\times 10^6$ and minimum loss tangents approaching $3\times 10^{-8}$, placing TeO${}_2$ among promising low-loss dielectrics for cryogenic microwave applications. Electron-spin-resonance spectroscopy further indicates a clean spin environment, while identifying distinct spin systems consistent with the known properties of the crystal.

arXiv comment10 pafes, 7 figures