Acquisition of Instrumentation for Cooling Semiconductor-based Low-Dimensional Electron Systems to T~1mK in a Large Magnetic Field

这笔赠款提供资金，用于购买加州理工学院的仪器，用于研究半导体中的低维关联电子系统。该仪器将允许在低至1mliKelvin的低温下对这些系统进行研究，这比目前的实践低了10倍。此外，该仪器将允许在低温下对样品施加高达16特斯拉的大磁场。需要在1毫升开尔文的温度或附近工作，这与现有半导体异质结构样品的质量和复杂性的稳步提高有关。这一趋势导致了许多与微妙的电子关联现象的接触，这些现象的彻底研究需要比传统的氦稀释制冷更低的温度。在1milliKelvin附近需要研究的现象中，突出的是所谓的偶分母分数量子化霍尔效应；最近发现的、但尚未预测的二维电子气在第一激发朗道能级中的绝缘相；以及强耦合极限下双层电子气的显著性质。后者特别有趣，因为它开始看起来好像这个系统是一个长期预测但难以捉摸的集体状态的例子，被称为激子超流体。当新的仪器解除了稀释制冷的技术限制时，有可能会有新的发现。这一仪器的获得将对加州理工大学研究生和本科生的教育产生影响。攻读博士学位的研究生将能够进行处于低维关联电子系统研究前沿的实验。学生将获得在低温/强磁场条件下工作所需的非常先进的实验技术的经验。这一技术经验将帮助他们在学术、国家实验室和工业环境中成功竞争工作。本科生，通过暑期研究和本学年的研究参与课程，也将能够使用这种新的仪器。在1毫开尔文温度范围内建立一台用于研究关联电子物理的最先进设备的前景已经吸引了小组中的学生的想象力。代表不足的少数民族和女性研究人员(研究生和本科生)参加了国家科学基金会资助的研究，她们的参与将继续下去。这种新的仪器将为这些学生提供重要的机会。

This grant provides funding to acquire instrumentation at the California Institute of Technology for research on low-dimensional correlated electron systems in semiconductors. The instrumentation will allow the investigation of these systems at low temperatures down to 1milliKelvin, a factor of ten below current practice. In addition, the instrumentation will allow large magnetic fields, up to 16 Tesla, to be applied to the samples at low temperatures. The need to work at, or near the temperature of 1milliKelvin is related to the steady improvement in the quality and complexity of the semiconductor heterostructure samples that are available. This trend has led to numerous encounters with subtle electron correlation phenomena whose thorough study demands lower temperatures than are available using conventional helium dilution refrigeration. Prominent among the phenomena requiring study near 1milliKelvin are the so called even-denominator fractional quantized Hall effects; the recently discovered, yet unpredicted, insulating phases of the 2 dimensional electron gas in the first excited Landau level; and the remarkable properties of bilayer electron gases in the strongly coupled limit. The latter is particularly interesting since it is beginning to appear as if this system is an example of a long-predicted, yet elusive, collective state known as an excitonic superfluid. There is the possibility of new discoveries when the technical limitation of the dilution refrigeration is lifted by the new instrumentation.This instrumentation acquisition will have impact the education of graduate and undergraduate students at Caltech. Graduate students, in pursuit of their Ph.D. degrees, will be able to perform experiments that are at the cutting edge of research on low-dimensional correlated electron systems. Students will become experienced with the very advanced experimental techniques needed to work in the low temperature/high magnetic field regime. This technical experience will help them successfully compete for jobs in the academic, national lab, and industrial environments. Undergraduate students, through both summer time research and research participation courses during the academic year, will also be able to work with this new instrumentation. The prospect of establishing a state-of-the-art apparatus for pursuing correlated electron physics into the 1milliKelvin temperature regime has already caught the imagination of the students in the group. Underrepresented minority and female researchers (both graduate and undergraduate students) have participated in the NSF-funded resarch and their participation will continue. This new instrumentation will provide important opportunities for these students.