Acquisition of a Compact Dilution Refrigerator

小行星9317417 这款紧凑型稀释制冷机用于弗吉尼亚大学在极低温度下探测先进材料和新型固态结构的电子和电动力学响应的实验。 这些研究项目的重点是电子隧穿，噪声和相互作用电子系统的基本基态和基本激发特性的传输研究。 由于全自旋、库仑和量子相关效应通常在~ 0.1K的温度下才变得明显，因此需要达到低于泵送液体3 H2（~ 0.3K）可达到的温度，因此必须使用稀释制冷机，该制冷机可以快速方便地达到约0.02K的基础温度。 预计稀释冰箱的正常使用将由三名主要研究者分担：Mark Lee教授（负责设施维护的主要用户）、Joseph Poon教授和Elias Towe教授。 Lee博士试图通过隧穿和噪声实验阐明0.1 K附近强相互作用区域中可变范围跳跃（弗赫）导体（如Si：P和PrBa 2Cu 3 O 7）的基态。 他还将使用稀释制冷机来研究高迁移率超导体-半导体结构中低温下的大规模量子相干性，以及新型超导体和正常金属之间的耦合如何能够洞察可能的非常规超导机制。 Poon博士对完全由金属原子组成的高度有序的新材料感兴趣，这些材料在低温下由于不寻常的对称性而表现出半导体或绝缘行为，如准晶或低维度。 对于这项工作，重要的是要有能力系统地测量电阻率下降到~ 0.03 K，以方便的方式，以确认和研究非金属行为的存在。 陶博士目前通过分子束外延生长高纯度半导体异质结构。 有效质量和迁移率的定量表征通常通过测量Shubnikov-de哈斯振荡和在非常低的温度下的霍尔效应量子化来完成。 陶博士的研究将包括不同晶体取向的异质结构迁移率的研究和氮化物基半导体异质结构的发展。 该仪器易于维护和操作，具有相对快速的冷却和样品周转时间，因此将作为固态和低温实验物理研究生和本科生的优秀教学工具。 稀释装置将安装在现有的4 He杜瓦瓶中，杜瓦瓶配备有补偿的10 T超导螺线管，并将与可操作的4 He可变温度低温恒温器共享泵送和气体支持设施。 ***

9317417 Lee This compact dilution refrigerator used in experiments probing the electronic and electrodynamic response of advanced materials and novel solid-state structures at very low temperatures at University of Virginia. These research projects focus on electron tunneling, noise, and transport studies of the fundamental ground-state and elementary excitation properties of interacting electron systems. Because full spin, Coulomb, and quantum correlation effects often do not become manifest until temperatures of ~ 0.1K, attainment of temperatures below those achievable by pumped liquid 3H2(~0.3 K) will be required, making necessary the use of a dilution refrigerator which can achieve a base temperature of approximately 0.02K in a rapid and convenient manner. It is anticipated that normal use of the dilution refrigerator will be divided among three principal investigators: Prof. Mark Lee, who will be the principal user responsible for the maintenance of the facility, Prof. Joseph Poon, and Prof. Elias Towe. Dr. Lee seeks to elucidate aspects of the ground state in variable range hopping (VRH) conductors such as Si:P and PrBa2Cu3O7 in the strongly interacting regime around 0.1 K by tunneling and noise experiments. He will also use the dilution refrigerator to investigate large scale quantum coherency at low- temperature in high mobility superconductor-semiconductor structures, and how the coupling between novel superconductors and normal metals can shed insight into possibly unconventional superconducting mechanisms. Dr. Poon is interested in highly ordered new materials, composed entirely of metal atoms, that show semiconducting or insulating behavior at low temperature as a result of unusual symmetries, as occurs in quasicrystals, or low dimensionality. For this work it is important to have the ability to systematically measure resistivities down to ~ 0.03 K in a convenient manner in order to confirm and study the existence of non-metallic behavior. Dr. Towe currently grows high purity semiconductor heterostructures by molecular beam epitaxy. Quantitative characterization effective masses and mobilities is typically done by measuring Shubnikov-de Haas oscillations and of the Hall effect quantization at very low temperatures. Dr. Towe's investigation will include a study of mobilities in heterostructures of varying crystallographic orientation and development of nitride-based semiconductor heterostructures. This instrument is straightforward to maintain and operate, has a relatively rapid cool-down and sample turn- around time, and will thus serve as an excellent teaching tool for graduate and undergraduate students in solid-state and low- temperature experimental physics. The dilution unit will be housed in an existing 4He dewar equipped with a compensated 10 T superconducting solenoid and will share pumping and gas support facilities with an operational 4He variable temperature cryostat. ***