论文标题
揭示了约瑟夫森电流引起的非线性terahertz响应中频率依赖性振荡
Revealing the frequency-dependent oscillations in the nonlinear terahertz response induced by the Josephson current
论文作者
论文摘要
超导体对强烈的Terahertz辐射的非线性反应一直是一个积极的研究边界。使用Terahertz Pump-Terahertz探针光谱法，我们研究了高温超导粉末的C轴非线性光学响应。在通过单周期Terahertz泵脉冲激发后，随着泵探针延迟的变化，探针脉冲的反射率振荡。有趣的是，振荡性中央频率与探针频率线性缩放，这一事实在泵探针实验中被广泛忽略。通过理论上解决界面上的非线性光学反射问题，我们表明我们的观察结果通过约瑟夫森型三阶非线性电动力学很好地解释了我们的观察，以及从材料内部到空间内部的发射系数。后者导致发射信号的强烈增强，其物理频率位于约瑟夫森等离子体边缘。我们的结果为相关量子材料的强场Terahertz光谱法提供了基准和新见解。
Nonlinear responses of superconductors to intense terahertz radiation has been an active research frontier. Using terahertz pump-terahertz probe spectroscopy, we investigate the c-axis nonlinear optical response of a high-temperature superconducting cuprate. After excitation by a single-cycle terahertz pump pulse, the reflectivity of the probe pulse oscillates as the pump-probe delay is varied. Interestingly, the oscillatory central frequency scales linearly with the probe frequency, a fact widely overlooked in pump-probe experiments. By theoretically solving the nonlinear optical reflection problem on the interface, we show that our observation is well explained by the Josephson-type third-order nonlinear electrodynamics, together with the emission coefficient from inside the material into free space. The latter results in a strong enhancement of the emitted signal whose physical frequency is around the Josephson plasma edge. Our result offers a benchmark for and new insights into strong-field terahertz spectroscopy of related quantum materials.
