MICROWAVE TRANSMISSION AND HARMONIC-GENERATION IN ANTIGRANULOCYTES HIGH-TC SUPERCONDUCTING FILMS - EVIDENCE FOR VISCOUS FLUX MOTION AND WEAK LINKS
MICROWAVE TRANSMISSION AND HARMONIC-GENERATION IN ANTIGRANULOCYTES HIGH-TC SUPERCONDUCTING FILMS - EVIDENCE FOR VISCOUS FLUX MOTION AND WEAK LINKS
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DOI：
10.1103/physrevb.43.10390
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发表时间：
1991-05-01
影响因子：
3.7
通讯作者：
SCHIEBER, M
中科院分区：
文献类型：
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作者：
GOLOSOVSKY, M;DAVIDOV, D;SCHIEBER, M
我们研究了在直流磁场H0和交变磁场H1 cos2-pi-f0t存在下，Y-Ba-Cu-O和Bi-Sr-Ca-Cu-O超导薄膜的微波传输。由于复电阻率的非线性响应，交变电场产生了许多谐波。微波在薄膜平面上与H0的传输取决于H0相对于微波电场的方向。我们通过实验发现，传输的场相关部分的行为类似于delta-tau-f的变化为\H0 sin-phi\。这表明存在宏观洛伦兹力，并强烈表明磁场中的复电阻率由粘-磁-动耗散机制主导。我们给出了一个简单的基于粘性通量运动的谐波产生模型。将实验与模型进行比较，可以估计Y-Ba-Cu-O薄膜在T = 70 K时，c轴方向上通量子的粘度系数-eta为eta = (2-4) X 10(-9) cgs单位。理论模型表明，eta的大小适合于弱钉住的Abrikosov通量子。含有内部约瑟夫森结的超导薄膜的直流输运特性受到微波辐射的强烈影响，因此，作为检测“薄弱环节”存在的诊断工具。高次谐波可以在所有类型的薄膜中产生，而与存在或不存在弱链接无关。然而，在弱环节存在的情况下，谐波产生的起始温度T(c)′低于微波传输变化的起始温度T(c)。一个基于薄膜粒度的简单模型可以解释这些观察结果。
We have studied the microwave transmission-tau through thin superconducting films of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O in the presence of a dc magnetic field H0 and an alternating magnetic field, H1 cos2-pi-f0t. The alternating field generates many harmonics due to the nonlinear response of the complex resistivity. The microwave transmission with H0 in the plane of the film depends on the orientation phi of H0 with respect to the microwave electric field. We found experimentally that the field-dependent part of the transmission behaves like delta-tau-f varies as\H0 sin-phi\. This indicates a macroscopic Lorentz force and strongly suggests that the complex resistivity in the magnetic field is dominated by a viscous-flux-motion dissipation mechanism. We demonstrate a simple model for the harmonic generation based on viscous fluxon motion. A comparison of the experiment with the model allows an estimate of the viscosity coefficient-eta for the fluxons in the direction of the c axis to be eta = (2-4) X 10(-9) cgs units for Y-Ba-Cu-O film at T = 70 K. Theoretical models suggest that the magnitude of eta is appropriate to weakly pinned Abrikosov fluxons. The dc transport properties of superconducting films containing internal Josephson junctions are strongly affected by microwave irradiation and serve, therefore, as a diagnostic tool to detect the presence of "weak links." Higher-order harmonics can be generated in all types of studied films independent of the presence or absence of weak links. However, in the presence of weak links, the onset temperature for the harmonic generation T(c)' is lower than the onset temperature for the change in the microwave transmission, T(c). A simple model based on the granularity of the film can explain these observations.