论文标题
地表约瑟夫森等离子波在高温超导体中
Surface Josephson plasma waves in a high-temperature superconductor
论文作者
论文摘要
电子密度振荡带有声性分散并维持在不同介质之间的边界上，提供了有关异质结构的表面和界面特性的信息。在超薄金属膜中，这些等离子激发受到严重抑制。预测超导性会减少耗散，从而允许检测这些共振。然而，在研究表面限制的约瑟夫森等离子体之前，已经研究了新兴的低损失界面库珀对波浪。在这里，我们报告了在高温超导体LA1.85SR0.15CUO4的超薄单晶膜中的产生和耦合。当用子隙THZ光子探测时，膜比临界温度低于临界温度的AU更明亮。我们表明，超导状态下的增强信号可以用比λ/3,000更好的空间分辨率可视化，源自光的近场耦合到表面约瑟夫森等离子体。我们的结果为对人工多层，拓扑异质结构中的埋入界面状态的增强超导性的非侵入性研究开辟了道路，以及约瑟夫森设备中的非线性现象。
Electron density oscillations with acoustic dispersions and sustained at boundaries between different media provide information about surface and interface properties of hetero-structures. In ultra-thin metallic films these plasmonic excitations are heavily damped. Superconductivity is predicted to reduce dissipation allowing detection of these resonances. Emerging low-loss interface Cooper-pair waves have been studied before, however, the observation of surface-confined Josephson plasmons has remained elusive. Here, we report on generation and coupling to these excitations in an ultrathin single-crystal film of high-temperature superconductor La1.85Sr0.15CuO4. The film becomes brighter than Au below the critical temperature when probed with sub-gap THz photons. We show that the enhanced signal in the superconducting state, which can be visualized with a spatial resolution better than λ/3,000, originates from near-field coupling of light to surface Josephson plasmons. Our results open a path towards non-invasive investigation of enhanced superconductivity in artificial multilayers, buried interface states in topological hetero-structures, and non-linear phenomena in Josephson devices.
