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O: Fachverband Oberflächenphysik
O 62: Poster: SrTiO3: A Versatile Material from Bulk Quantum Paraelectric to 2D Superconductor (joint session TT/KFM/MA/O)
O 62.3: Poster
Wednesday, March 20, 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