Abstract
Planar superconducting resonators are now being increasingly used at mK temperatures in a number of novel applications. We have experimentally investigated three types of niobium resonators including a lumped-element design fabricated on sapphire and SiO2/Si substrates. They all exhibit a nonmonotonic temperature dependence of their center frequency which could be accurately described by resonant absorption by two-level fluctuators (TLF). By analyzing the temperature dependence we extracted information about the distribution of TLF. Our results are consistent with there being a spread of TLF at the interface between superconductor and substrate.
Original language | English |
---|---|
Pages (from-to) | 132501 |
Number of pages | 1 |
Journal | Physical Review B |
Volume | 80 |
Issue number | 13 |
DOIs | |
Publication status | Published - 1 Oct 2009 |