Taherian N, Först M, Liu A, Fechner M, Pavicevic D, von Hoegen A, Rowe E, Liu Y, Nakata S, Keimer B, Demler E, Michael M H, Cavalleri A
Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany.
Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
NPJ Quantum Mater. 2025;10(1):54. doi: 10.1038/s41535-025-00776-1. Epub 2025 Jun 6.
The nonlinear driving of collective modes in quantum materials can lead to a number of striking non-equilibrium functional responses, which merit a comprehensive exploration of underlying dynamics. However, the coherent coupling between nonlinearly-driven modes frequently involves multiple mode coordinates at once, and is often difficult to capture by one-dimensional pump probe spectroscopy. One example is phonon-mediated amplification of Josephson plasmons in YBaCuO, a phenomenon likely associated with the mysterious superconducting-like optical response observed in this material. Here, we report two-dimensional nonlinear spectroscopy measurements in driven YBaCuO. We excite apical oxygen phonons with of mutually-delayed carrier envelope phase stable mid-infrared pump pulses, and detect time-modulated second-order nonlinear optical susceptibility. We find that the driven phonons parametrically amplify coherent pairs of fluctuating opposite-momentum Josephson plasma polaritons, corresponding to a squeezed state of the Josephson plasma.
量子材料中集体模式的非线性驱动可导致许多引人注目的非平衡功能响应，这值得对其潜在动力学进行全面探索。然而，非线性驱动模式之间的相干耦合常常同时涉及多个模式坐标，并且通常难以通过一维泵浦探测光谱法来捕捉。一个例子是YBaCuO中声子介导的约瑟夫森等离子体激元放大，这一现象可能与在这种材料中观察到的神秘的类超导光学响应有关。在此，我们报告了在受驱动的YBaCuO中的二维非线性光谱测量。我们用相互延迟的载波包络相位稳定的中红外泵浦脉冲激发顶角氧声子，并检测时间调制的二阶非线性光学磁化率。我们发现，受驱动的声子参量放大了波动的反动量约瑟夫森等离子体极化激元的相干对，这对应于约瑟夫森等离子体的压缩态。
