2019/11/26 by Vincent T. Engl, Nikolaj G. Ebensperger, Engl, Vincent T. +5 · 1 citation
Materials Science · Engineering · #Electronic and Structural Properties of Oxides #Ferroelectric and Piezoelectric Materials #Acoustic Wave Resonator Technologies
paper · pdf · doi:10.48550/arxiv.1911.11456
The complex dielectric constant ε = ε1 + i ε2 of SrTiO3 reaches high values ε1 ≈ 2*104 at cryogenic temperatures, while the dielectric losses (ε2) are much stronger than for other crystalline dielectrics. SrTiO3 is a common substrate for oxide thin films, like the superconducting LaAlO3/SrTiO3 system, but the large ε1 and ε2 restrict high-frequency quantum devices on SrTiO3. Here we present superconducting coplanar Nb resonators on SrTiO3, which we successfully operate in a distant-flip-chip geometry at frequencies that exceed 1 GHz. We find a pronounced and unexpected increase in resonator quality factor Q at temperatures below 1 K, reaching up to Q ≈ 800. We attribute this to substantial changes of the dielectric losses in SrTiO3 at mK temperatures, and we also detect non-monotonous changes in the temperature-dependent ε1. These findings challenge our present understanding of the dielectric properties of SrTiO3 and at the same time demonstrate that cryogenic high-frequency devices on SrTiO3 are more feasible than previously assumed.