Terahertz Second-Harmonic Generation from Lightwave Acceleration of Symmetry-Breaking Nonlinear Supercurrents
Terahertz Second-Harmonic Generation from Lightwave Acceleration of Symmetry-Breaking Nonlinear Supercurrents
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DOI：
10.1103/physrevlett.124.207003
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发表时间：
2020-05-19
影响因子：
8.6
通讯作者：
Wang, J.
中科院分区：
文献类型：
--
作者：
Vaswani, C.;Sundahl, C.;Wang, J.
我们报告太赫兹（THz）光诱导的二次谐波产生，在超导体的反转对称性，禁止偶数阶非线性。THz二次谐波发射在超导体临界温度以上消失，并产生于扭曲的安德森赝自旋在多频太赫兹驱动频率的进动，这是不允许的平衡对称性。我们解释了微观物理的动力学对称性破缺原理在亚太赫兹周期，通过使用量子动力学模型之间的相互作用的强太赫兹光波的非线性和脉冲传播。与直流偏置超导体相比，超导体内部的非零积分脉冲区域由于子周期库珀对加速而导致光致非线性超电流，而直流偏置超导体可以通过超导带隙下方的能带结构和THz驱动场来控制。
We report terahertz (THz) light-induced second harmonic generation, in superconductors with inversion symmetry that forbid even-order nonlinearities. The THz second harmonic emission vanishes above the superconductor critical temperature and arises from precession of twisted Anderson pseudospins at a multicycle, THz driving frequency that is not allowed by equilibrium symmetry. We explain the microscopic physics by a dynamical symmetry breaking principle at sub-THz-cycle by using quantum kinetic modeling of the interplay between strong THz-lightwave nonlinearity and pulse propagation. The resulting nonzero integrated pulse area inside the superconductor leads to light-induced nonlinear supercurrents due to subcycle Cooper pair acceleration, in contrast to dc-biased superconductors, which can be controlled by the band structure and THz driving field below the superconducting gap.