Low vibration and low temperature closed-cycle cryostat for oxide MBE and laser-ARPES

用于氧化物 MBE 和激光 ARPES 的低振动和低温闭环低温恒温器

• 批准号: RTI-2020-00634
• 负责人: Sawatzky, George
• 金额: $ 10.93万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=693783
• 关键词: Low; vibration; low; temperature; closed

This proposal is for the purchase of a closed-cycle recirculating chiller to upgrade the low temperature cryostat of the Quantum Materials and Devices Foundry (QMDF) led by George Sawatzky at UBC. The goal of the facility is to study the properties of materials comprised of layers of different compounds known as heterostructures, and phenomena arising at the interfaces between these layers. In particular, QMDF aims at engineering transition-metal oxide and dichalcogenide heterostructures, growing them by molecular beam epitaxy (MBE), and to comprehensively characterizing them in situ as they are being fabricated layer-by-layer. While QMDF will be used to explore a large number of phenomena, the immediate goal is to study unconventional superconductivity in thin film iron pnictides and nickelates, as they might be the key materials to answer the most intriguing question in modern condensed matter: what is the nature of unconventional superconductivity and how to create a room temperature superconductor. *******The cryostat to be upgraded is used for mapping of electronic bands in heterostructures by means of angle resolved photoemission spectroscopy (ARPES), the main characterization method associated with the facility. Unlocking the mystery of high-temperature superconductivity might be hiding in subtle details of the electronic band structure, and it is imperative to gain information with high signal to noise ratio and high energy and momentum resolution. In turn, this requires the samples under investigation to be held at cryogenic temperatures for an extended time while under study. The challenge is to find a cost-effective method of keeping the sample stable to better than 0.1K at all cryogenic temperatures down to 3K.*******Low temperature experiments today can be undertaken using two methods: (1) the direct use of liquid helium (flow cryostat, currently used); or (2) the use of a closed cycle refrigeration system. While the latter allows us to reach lower temperatures using pumped helium, it cannot run constantly for more then a few days, is prone to sample temperature and position drift, and is exorbitantly expensive to run. On the one hand, a typical ARPES facility equipped with a flow cryostat costs about $100,000/year consuming one of the earth's most precious and non-renewable resources, releasing much of it back into the atmosphere. On the other hand, a typical closed cycle cryostat is not able to operate below about 10K. Our goal, is to combine the technological advances in cryogenic design that will allow UBC's flow cryostat to reach very low temperatures with a cryogen free refrigeration system produced by Janis Research Company.*******This upgrade will provide the Quantum Materials and Devices Foundry with dramatically increased experimental running times, which are essential for accurately measuring the electronic properties of some of the new exotic samples that are now being routinely grown at UBC.

这项提案是为了购买一台闭路循环冷冻机，以升级由UBC的George Sawatzky领导的量子材料和器件铸造厂(QMDF)的低温恒温器。该设备的目标是研究由称为异质结构的不同化合物层组成的材料的性质，以及这些层之间的界面上出现的现象。特别是，QMDF的目标是设计过渡金属氧化物和二卤化物异质结构的工程化，通过分子束外延(MBE)生长它们，并在逐层制造的过程中对它们进行原位综合表征。虽然QMDF将被用来探索大量的现象，但近期的目标是研究铁离子和镍酸盐薄膜中的非常规超导电性，因为它们可能是回答现代凝聚态物质中最有趣的问题的关键材料：非常规超导电性的本质是什么，以及如何创造室温超导体。*将升级的低温恒温器用于通过角度分辨光电子能谱(ARPES)绘制异质结构中的电子能带图，这是与该设施相关的主要表征方法。解开高温超导的奥秘可能隐藏在电子能带结构的细微细节中，获取高信噪比、高能量和动量分辨率的信息势在必行。反过来，这要求研究中的样品在研究期间在低温下保持较长时间。挑战是找到一种经济有效的方法，使样品在所有低温温度降至3K以下时稳定在0.1K以上。今天的低温实验可以使用两种方法：(1)直接使用液氦(目前使用的流动低温恒温器)；或(2)使用闭路循环制冷系统。虽然后者允许我们使用抽运的氦达到较低的温度，但它不能连续运行几天以上，容易受到样品温度和位置漂移的影响，而且运行成本过高。一方面，一个典型的配备流动低温恒温器的ARPES设施每年的成本约为10万美元，消耗了地球上最宝贵和不可再生的资源之一，将其中大部分释放到大气中。另一方面，典型的闭合循环低温恒温器不能在10K以下运行。我们的目标是将低温设计方面的技术进步与Janis Research Company生产的无制冷剂制冷系统相结合，这将使UBC的流动低温恒温器达到非常低的温度。*这次升级将为量子材料和器件铸造厂提供显著增加的实验运行时间，这对于准确测量一些现在正在UBC常规生长的新的外来样品的电子性质至关重要。