Localization and pair breaking parameter in superconducting molybdenum nitride thin films
Localization and pair breaking parameter in superconducting molybdenum nitride thin films
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DOI：
10.1088/0953-8984/29/1/015701
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发表时间：
2017-01
期刊：
影响因子：
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通讯作者：
T. Tsuneoka;K. Makise;S. Maeda;B. Shinozaki;F. Ichikawa
中科院分区：
文献类型：
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作者：
T. Tsuneoka;K. Makise;S. Maeda;B. Shinozaki;F. Ichikawa
我们研究了在氧化镁衬底上沉积氮化钼薄膜的超导-绝缘体转变。从局域化理论出发，用芬克尔斯坦公式很好地解释了厚膜从≈6.6K开始的T_c随正常态方阻RsQ_N的增大而降低的现象。目前的分析表明，超导-绝缘体转变发生在临界方阻Rc≈2kΩ处。结果表明，Rc以上的Rsq(T)在RcRqN和Rq上分别表现出Rsq(T)=Rsq，0−alnT和Rsq(T)∝exp[(T0/T)1/2]的不同特征，其中Rsq，0为经典剩余电阻，A为常数。由热涨落引起的超额电导σ‘(T)由Aslamazov-Larkin和Maki-Thompson修正项之和以及后一项的对断参数δ来分析。虽然δ的RSQN依赖关系的实验结果，即δ∝(RSQN)≈1.7与局域化理论导出的线性关系δ∝(RSQN)不一致，但总和与数据符合得很好。
We have investigated the superconductor-insulator transition in molybdenum nitride films prepared by deposition onto MgO substrates. It is indicated that the Tc depression from ≈6.6 K for thick films with increase of the normal state sheet resistance RsqN was well explained by the Finkel’stein formula from the localization theory. Present analysis suggests that the superconducting-insulator transition occurs at a critical sheet resistance Rc≈2 kΩ. It is found that the Rsq(T) above Rc shows different characteristics of Rsq(T)=Rsq,0−AlnT and Rsq(T)∝exp[(T0/T)1/2] in the regions RcRsqN>RQ, respectively, where Rsq,0 is the classical residual resistance and A is a constant. The excess conductance σ′(T) due to thermal fluctuation has been analyzed by the sum of the Aslamazov–Larkin and Maki–Thompson correction terms with use of the pair breaking parameter δ in the latter term. The sum agrees well with the data, although the experimental results of the RsqN dependence of δ, that is, δ∝(RsqN)≈1.7 shows the disagreement with a linear relation δ∝(RsqN) derived from the localization theory.