论文标题
在金属 - 绝缘体转变附近的超导体中的异常高温THZ非线性
Anomalous high-temperature THz nonlinearity in superconductors near the metal-insulator transition
论文作者
论文摘要
强障碍和超导性的相互作用是对凝结物理学的长期兴趣的话题。在这里，我们探索了接近3D金属胰蛋白过渡的超导NBN膜的非线性THZ响应。对于最小无序的样品，非线性$χ^{（3）} $响应的大小遵循预期的超流体密度的温度依赖性。相比之下，对于金属 - 绝缘体过渡附近的高混乱样本，$χ^{（3）} $非线性仍然存在于最清洁样品的$ T_C $的4倍。我们讨论了这种非常大的非线性的可能起源，包括它在接近本地化的超导性温度尺度的增强中产生的可能性。我们的工作强调了有限频率非线性THZ实验在检测超导相关性的重要性，即使是在远程有序超导性不持续存在的区域中。
The interplay of strong disorder and superconductivity is a topic of long-term interest in condensed matter physics. Here we explore the nonlinear THz response of superconducting NbN films close to the 3D metal-insulator transition. For the least disordered samples, the magnitude of the nonlinear $χ^{(3)}$ response follows the temperature dependence of the superfluid density as expected. In contrast, for high disorder samples near the metal-insulator transition the $χ^{(3)}$ nonlinearity persists to temperatures as high as even 4 times the $T_c$ of the cleanest sample. We discuss the possible origins of this remarkably large nonlinearity, including the possibility that it arises in an enhancement of the temperature scales of superconductivity close to localization. Our work highlights the importance of finite frequency nonlinear THz experiments in detecting superconducting correlations even into regions where long-range ordered superconductivity does not persist.
