We present the measurements of the temperature dependence of the internal quality factor （O,i） of a microwave resonator, well below the superconducting transition temperature. The device is a quarter-wavelength niob...We present the measurements of the temperature dependence of the internal quality factor （O,i） of a microwave resonator, well below the superconducting transition temperature. The device is a quarter-wavelength niobium （Tc = 9.2 K） coplanar waveguide resonator. The measured ｜S21｜ parameter shows typically the skewed Lorentzian distributions, from which the fitted quality factor monotonically decreases with the temperature increasing from 30ink to 900mK. It is observed that for the lower temperature range （i.e., at T 〈 700 mK） the temperature dependence of the fitted Qi deviates significantly from the predictions of the usual Mattis-Bardeen theory. The measured 3 dB internal quality factor Qi also verifies such an anomalous temperature dependence. Physically, this phenomenon could be attributed dominantly to the effects of the two-level systems in the device, rather than the usual temperature-dependent complex conductance.展开更多
We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates.Their microwave transmissions are measured at 20 mK....We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates.Their microwave transmissions are measured at 20 mK.It is found that these two types of resonators possess significantly different loaded quality factors;one is 5.6×10^(3) and the other is 4.0×10^(4).The measured data are fitted well by classical ABCD matrix approach and consequently the coupling capacitances are determined.It is found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.展开更多
基金Supported by the State Key Development Program for Basic Research of China under Grant No 2011CB923104, the National Natural Science Foundation of China under Grant Nos 61301031, 11174373 and U1330201.
文摘We present the measurements of the temperature dependence of the internal quality factor （O,i） of a microwave resonator, well below the superconducting transition temperature. The device is a quarter-wavelength niobium （Tc = 9.2 K） coplanar waveguide resonator. The measured ｜S21｜ parameter shows typically the skewed Lorentzian distributions, from which the fitted quality factor monotonically decreases with the temperature increasing from 30ink to 900mK. It is observed that for the lower temperature range （i.e., at T 〈 700 mK） the temperature dependence of the fitted Qi deviates significantly from the predictions of the usual Mattis-Bardeen theory. The measured 3 dB internal quality factor Qi also verifies such an anomalous temperature dependence. Physically, this phenomenon could be attributed dominantly to the effects of the two-level systems in the device, rather than the usual temperature-dependent complex conductance.
基金Supported by the National Natural Science Foundation of China under Grant No 11174373the National Basic Research Program of China under Grant No 2010CB923104.
文摘We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates.Their microwave transmissions are measured at 20 mK.It is found that these two types of resonators possess significantly different loaded quality factors;one is 5.6×10^(3) and the other is 4.0×10^(4).The measured data are fitted well by classical ABCD matrix approach and consequently the coupling capacitances are determined.It is found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.
