Frequency dependence of the surface impedance of YBa2Cu3O7- delta thin films in a dc magnetic field: Investigation of vortex dynamics.
Frequency dependence of the surface impedance of YBa2Cu3O7- delta thin films in a dc magnetic field: Investigation of vortex dynamics.
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直流磁场中 YBa2Cu3O7-δ 薄膜表面阻抗的频率依赖性：涡流动力学研究。
DOI：
10.1103/physrevb.50.1178
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Dresselhaus
中科院分区：
文献类型：
--
作者：
Revenaz;Oates;Labbé;Dresselhaus
我们报告了使用带状线谐振器在外部施加的直流磁场 B（平行于 c 轴）中 YBa 2 Cu 3 O 7− δ 薄膜的表面阻抗 Z s= R s+ iωλ' 的测量。在 T= 4.3 K 时，我们获得表面电阻 R s 和微波穿透深度 λ’，作为施加高达 5 T 的直流场的函数，以及作为从 1.2 到 20 GHz 的微波频率 f 的函数。虽然在所有频率下，当 B> 1 T 时，λ' 随 B 线性增加，但发现 R s 大致为 ∝ B α (f)，其中，对于 f≤ 10 GHz，α (f)< 1；对于 f≥ 10 GHz，α (f)≊ 1。在零直流场中，R s∝ f 2。对于 B> 1 T，R s 对 f 的依赖性要弱得多。 Z s (f, T, B) 的结果已使用 Coffey 和 Clem 开发的模型进行了定量解释，该模型基于涡动力学的自洽处理，包括涡旋钉扎、粘性阻力和通量蠕变的影响。通过拟合过程得到钉扎力常数α p 、钉扎频率ω p 和钉扎活化能U 0 (T,B)。我们发现 4.3 K 时热激活焊剂蠕变对表面电阻的影响非常显着。我们确定的低 U 0≊ 35 K 被解释为由涡晶格与密集随机钉扎势的相互作用产生，如集体钉扎理论中所述。
We report measurements of the surface impedance Z s= R s+ iωλ’of YBa 2 Cu 3 O 7− δ thin films in an externally applied dc magnetic field B (parallel to the c axis) using a stripline resonator. At T= 4.3 K we obtain the surface resistance R s and the microwave penetration depth λ’as a function of applied dc field up to 5 T and as a function of microwave frequency f from 1.2 to 20 GHz. While λ’increases linearly with B for B> 1 T at all frequencies, R s is found to be roughly∝ B α (f), where α (f)< 1 for f≤ 10 GHz and α (f)≊ 1 for f≥ 10 GHz. In zero dc field, R s∝ f 2. For B> 1 T, R s shows a much weaker dependence on f. The results for Z s (f, T, B) have been quantitatively explained using a model developed by Coffey and Clem, based on a self-consistent treatment of vortex dynamics that includes the influence of vortex pinning, viscous drag, and flux creep. The pinning force constant α p, the pinning frequency ω p, and the pinning activation energy U 0 (T, B) are obtained through the fitting procedure. We find that the effects of thermally activated flux creep at 4.3 K upon the surface resistance are significant. The low U 0≊ 35 K that we determine is interpreted as arising from the interaction of the vortex lattice with a dense random pinning potential as described in the collective-pinning theory.