Browsing by Author "Lai, LS"

Now showing 1 - 2 of 2

Microwave properties of a Y0.7Ca0.3Ba2Cu3O7-delta inicrostrip ring resonator with various hole concentrations
(2004-10-15)
Lai, LS
;
Juang, JY
;
Wu, KH
;
Uen, TM
;
Lin, JY
Superconducting ring resonator with a Y0.7Ca0.3Ba2Cu3O7-delta ground plane was fabricated by using Y0.7Ca0.3Ba2Cu3O7-delta thin film deposited on both sides of a LaAlO3 (LAO) substrate. The resonator exhibits a high quality factor Q > 10(4) at T < 30 K, and from empirical relation,T-c/T-c,T-max = 1 - 82.6(p - 0.16)(2), we obtained the hole concentration p. By controlling the oxygen contents of the ring resonator, the hole concentration p was controlled from 0.218 to 0.088, determined by the empirical relation, in the same film. The temperature dependence of the resonance frequency, f(T), was then systematically studied. By using Chang's inductive formula and taking a functional form (lambda(5K)/lambda (T))(2) = 1 - (T/T-c)(2) at T < 0.6T(c), the London penetration depths lambda(5K) for various oxygen contents at 5K were obtained, respectively. Finally, it allows us to test the Uemura relation 1 /lambda(2)(5K) proportional to T-c from the over- to the underdoped regime in the same sample. (C) 2004 Elsevier B.V. All rights reserved.
Temperature dependence of superfluid YBa2Cu3O7-delta and Y0.7Ca0.3Ba2Cu3O7-delta density in thin films: A doping dependence study of the linear slope
(2005-11-01)
Lai, LS
;
Juang, JY
;
Wu, KH
;
Uen, TM
;
Gou, YS
By using a microstrip ring resonator to measure the temperature dependence of the in-plane magnetic penetration depth lambda(T) in YBa2Cu3O7-delta (YBCO) and Y0.7Ca0.3Ba2Cu3O7-delta (Ca-YBCO) epitaxially grown thin films, the linear temperature dependence of the superfluid density rho(s)/m* &3bond; I/lambda(2)(T) was observed from the under- to the overdoped regime at the temperatures below T/T-c approximate to 0.3. For the underdoped regime of YBCO and Ca-YBCO thin films, the magnitude of the slope d(1/lambda(2)(T))/dT is insensitive to doping, and it can be treated in the framework of projected d-density-wave model. Combining these slope values with the thermal conductivity measurements, the Fermi-liquid correction factor alpha(2) from the Fermi-liquid model, suggested by Wen and Lee, was revealed here with various doping levels. (c) 2005 Elsevier B.V. All rights reserved.