Closed-Cycle Magnetic Cryostat with a tuneable open cavity for spectroscopy applications

新型闭环低温恒温器结合了样品温度在4 K和300 K之间，磁场达到9 T时的高度空间分辨自由空间光谱，是本提案的核心设备。该低温恒温器将在奥尔登堡大学量子材料小组的研究活动中发挥重要作用。这对于探索新型量子材料、TMDC单层和范德华异质结构以及光-物质耦合杂化系统的光学和磁光性质至关重要。该小组的核心研究活动之一是研究光学微腔中光与物质之间强光-物质耦合机制的演变效应。在这种耦合的光-物质系统中，激子-极化子以混合激发的形式演化。极化子物理学是一个具有高度当代相关性的研究领域，因为它具有直接的应用相关性（新型相干光源），并且具有很强的基础重要性，例如在集体激发和相变的研究中。为了优化和研究量子材料在腔量子电动力学实验中的应用，需要一种测量系统，它可以在低温下实现高度空间分辨的自由空间光谱。低温恒温器需要提供大磁场，并有可能建立一个所谓的开放腔。特别是后者，它要求抑制系统中几乎所有的振动。作为量子材料研究小组的核心设备，它将为奥尔登堡大学内外的各种合作打开大门。

The new Closed-Cycle Cryostat, which combines highly spatially resolved free-space spectroscopy at sample temperatures between 4 K and 300 K and at magnetic fields reaching 9 T is the central equipment of this proposal. This cryostat will have an exposed role in the research activities of the Quantum Materials group at the University of Oldenburg. It will be essential for exploring the optical- and magneto-optical properties of novel quantum materials, TMDC monolayers and van-der-Waals heterostructures, as well as light-matter coupled hybrid systems. One of the central research activities of the group is the investigation of effects evolving in the regime of strong light-matter coupling between light- and matter in optical microcavities. In such coupled light-matter systems, exciton-polaritons evolve as hybrid excitations. The physics of polaritons is a research area of high contemporary relevance, as it has a direct application relevance (novel coherent light sources) and furthermore is of strong fundamental importance, e.g. in the investigation of collective excitations and phase transitions. In order to optimize and investigate quantum materials for their applications in cavity quantum electrodynamics experiments, a measurement system is required, which enables highly spatially resolved free space spectroscopy down to cryogenic temperatures. The cryostat needs to provide large magnetic fields, and the possibility to set up a so-called open cavity. It is in particular the latter, which demands a suppression of nearly all vibrations in the system. As a central piece of equipment of the quantum materials research group, it will open the door for a variety of collaborations within the university of Oldenburg and beyond.