纳米沟槽Nb薄膜中磁通导引与霍尔效应的相互作用
Interplay of flux guiding and Hall effect in Nb films with nanogrooves
摘要：
通过四探针测量和相应的理论模型，研究了具有周期性排列纳米凹槽的超导Nb薄膜中涡旋导向和霍尔效应之间的相互作用.纳米凹槽被聚焦离子束研磨，并诱导出搓板型的对称钉扎电位。薄膜的电阻率张量是在接近于临界温度的温度下在小电流密度的限制下确定的，该温度用于相对于钉扎纳米尺度的涡旋晶格的基本匹配配置。电流方向相对于凹槽之间的角度在$0^\circ$和$90^\circ$之间设置为七个固定值。在$T_c$附近的一个很窄的温度范围内，观察到的霍尔电阻率$ρ_\perp^-$的温度依赖性的符号变化。相比之下，对于所有的纳米图案化的薄膜$ρ_\perp^-$是非零的，在一个更广泛的温度范围内低于$T_c$，使我们能够区分两个贡献之间的$ρ_\perp^-$，即一个贡献源于引导涡旋运动和另一个造成的霍尔异常，就像在生长的Nb膜。所有四个测得的电阻率分量成功地拟合到解析表达式内的竞争各向同性和各向异性钉扎的随机模型的框架。这提供了证据的模型有效性的描述超导薄膜的电阻响应与搓板钉扎纳米景观。
英文摘要：
The interplay between vortex guiding and the Hall effect in superconducting Nb films with periodically arranged nanogrooves is studied via four-probe measurements in standard and Hall configurations and accompanying theoretical modeling. The nanogrooves are milled by focused ion beam and induce a symmetric pinning potential of the washboard type. The resistivity tensor of the films is determined in the limit of small current densities at temperatures close to the critical temperature for the fundamental matching configuration of the vortex lattice with respect to the pinning nanolandscape. The angle between the current direction with respect to the grooves is set at seven fixed values between $0^\circ$ and $90^\circ$. A sign change is observed in the temperature dependence of the Hall resistivity $ρ_\perp^-$ of as-grown films in a narrow temperature range near $T_c$. By contrast, for all nanopatterned films $ρ_\perp^-$ is nonzero in a broader temperature range below $T_c$, allowing us to discriminate between two contributions in $ρ_\perp^-$, namely one contribution originating from the guided vortex motion and the other one caused by the Hall anomaly just as in as-grown Nb films. All four measured resistivity components are successfully fitted to analytical expressions derived within the framework of a stochastic model of competing isotropic and anisotropic pinning. This provides evidence of the model validity for the description of the resistive response of superconductor thin films with washboard pinning nanolandscapes.
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