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TT: Fachverband Tiefe Temperaturen

TT 58: SrTiO₃: A Versatile Material from Bulk Quantum Paraelectric to 2D Superconductor: Poster (joint session TT/KFM/MA/O)

TT 58.3: Poster

Mittwoch, 20. März 2024, 15:00–18:00, Poster E

Low-temperature GHz response of quantum paraelectrics SrTiO₃ and KTaO₃ — Vincent T. Engl, Nikolaj G. Ebensperger, Cenk Beydeda, Lars Wendel, Marius Tochtermann, Ilenia Neureuther, Ishan Sarvaiya, Martin Dressel, and •Marc Scheffler — 1. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany

The low-temperature dielectric properties of SrTiO₃ and KTaO₃ are characteristic of their quantum paraelectric nature: upon cooling, the real part є₁ of the dielectric function strongly increases, but eventually levels off at high values of ≈ 20000 for SrTiO₃ and ≈ 4000 for KTaO₃. In particular for SrTiO₃ it is very demanding to combine such dielectric bulk material with conventional GHz circuitry. We present superconducting coplanar Nb resonators on SrTiO₃ and KTaO₃ substrates, where in the case of SrTiO₃ we employ a distant flip chip geometry. Taking advantage of several resonator modes, we determine the dielectric properties of the two materials at frequencies around 1 GHz and at temperatures down to 25 mK. We thus access regimes of frequency and temperatures, where the dielectric properties of SrTiO₃ and KTaO₃ have barely been studied.

For the case of SrTiO₃, we find an unexpected temperature dependence of the real part є₁ of the dielectric constant: at temperatures below 5 K, where є₁ is expected to vary little upon further cooling, we find a clear maximum around 3 K and a weak minimum around 200 mK. We also observe a strong suppression of microwave losses in both SrTiO₃ and KTaO₃ for temperatures down to the mK range.

Keywords: SrTiO3; KTaO3; quantum paraelectric; microwave resonators; GHz dielectrics