Superconducting magnet cryostat system for terahertz spectroscopy

Lange教授所要求的超导磁体低温恒温器系统允许研究太赫兹(THz)光谱范围内的超强和深强轻质耦合腔量子电动力学(c-QED)结构。通过定量的、无参数的数值模拟来定制THz模的近场，我们团队设计和制造了用于c-QED实验的光-物质耦合结构，以及能够在原子强场下进行THz实验的近场增强谐振器。电磁场的这种亚波长控制对于我们团队的目标是研究光与物质相互作用的极端极限，其中光学非线性发生在比单个光周期短得多的时间尺度上，在这一目标中发挥着核心作用。最近的研究亮点包括超越科恩定理的朗道电子的非线性，动态布洛赫振荡和高次谐波产生的观测，拓扑绝缘体中狄拉克电子的光波加速，天线增强THz近场中的最小耗散自旋开关，可切换THz谐振器中深-强光耦合电子的非绝热控制，以及超强耦合共振的载波Rabi翻转的观测。所需的磁冷柜将使我们能够继续这一研究，并探索凝聚态系统中THz亚循环物理的新方向。该系统的主要特点包括高达6T的磁场，同时提供与45°打开角度相对应的非常大的对称光学孔径，允许在焦平面内进行紧密聚焦，从而获得强大的太赫兹场幅。这些性质将使我们能够研究磁场中的强场THz动力学，这特别涉及到我们的朗道极化c-QED系统。在这里，我们的目标是以前无法达到的光-物质耦合强度，其中真空拉比频率显著超过光的载波频率。此外，我们将探索新的c-QED概念，包括超导谐振器或原子薄材料，如过渡金属二卤化物，在磁场中。从线性动力学过渡到非微扰非线性动力学，我们期望揭示新的现象，包括高阶非线性，非经典光的产生，腔极化子的非线性相互作用产生的共振，或相变。

The superconducting magnet cryostat system requested by the group of Prof. Lange allows for the investigation of ultrastrongly and deep-strongly light-matter coupled cavity quantum electrodynamical (c-QED) structures in the terahertz (THz) spectral range. Tailoring near fields of THz modes by quantitative, parameter-free numerical simulations, our group designs and fabricates light-matter coupled structures for c-QED experiments, as well as near-field enhancing resonators enabling THz experiments with atomically strong fields. This subwavelength control of electromagnetic fields plays a central role for our group’s aim to investigate extreme limits of light-matter interaction in which optical nonlinearities occur on time scales significantly shorter than a single cycle of light. Recent research highlights include nonlinearities of Landau electrons beyond Kohn’s theorem, the observation of dynamical Bloch oscillations and high-harmonics generation, lightwave acceleration of Dirac electrons in topological insulators, minimally dissipative spin switching in antenna-enhanced THz near fields, non-adiabatic control of deep-strongly light-matter coupled electrons in switchable THz resonators, and the observation of carrier-wave Rabi flopping of ultrastrongly coupled resonances.The requested magnet cryostat will allow us to continue this research and explore novel directions of THz subcycle physics in condensed-matter systems. The system’s key features include magnetic fields of up to 6 T while providing an exceptionally large and symmetric optical aperture corresponding to an opening angle of 45°, permitting tight focusing and thus strong THz field amplitudes, in the focal plane. These properties will enable the investigation of strong-field THz dynamics in magnetic fields, which in particular concerns our Landau polariton c-QED systems. Here, we aim for previously inaccessible light-matter coupling strengths, where the vacuum Rabi frequency significantly exceeds the carrier frequency of light. Furthermore, we will explore novel c-QED concepts including superconducting resonators or atomically thin materials such as transition metal dichalcogenides, in magnetic fields. Transitioning from linear to non-perturbatively nonlinear dynamics, we expect to unveil novel phenomena including high-order nonlinearities, generation of non-classical light, resonances generated by nonlinear interactions of cavity polaritons, or phase transitions.