Superconducting magnet cryostat system for terahertz spectroscopy

Lange教授小组要求的超导磁体低温恒温系统允许在太赫兹（THz）光谱范围内研究超强和深强光-物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裁剪太赫兹模式的近场，我们的团队设计并制造了用于c-QED实验的光-物质耦合结构，以及近场增强谐振器，使太赫兹实验具有原子强场。这种对电磁场的亚波长控制对于我们小组研究光-物质相互作用的极端极限的目标起着核心作用，其中光学非线性发生在明显短于光的单周期的时间尺度上。最近的研究重点包括朗道电子超越Kohn定理的非线性、动态Bloch振荡和高次谐波产生的观察、拓扑绝缘体中Dirac电子的光波加速、天线增强太赫兹近场中最小耗散自旋开关、可切换太赫兹谐振器中深强光-物质耦合电子的非绝热控制。以及对超强耦合共振的载波拉比跳变的观测。所要求的磁体低温恒温器将使我们能够继续这项研究并探索凝聚态系统中太赫兹亚循环物理的新方向。该系统的主要特点包括高达6 T的磁场，同时提供一个超大的对称光学孔径，对应于45°的开口角，允许紧密聚焦，因此在焦平面上具有强太赫兹场振幅。这些特性将有助于研究磁场中的强场太赫兹动力学，特别是我们的朗道极化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着超过光的载流子频率。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，如过渡金属二硫族化物，在磁场中。从线性到非摄动非线性动力学的转变，我们期望揭示新的现象，包括高阶非线性，非经典光的产生，由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.