Acquisition of a Dilution Refrigerator and High Field Solenoid System for Millikelvin Scanning Probe Microscopy Studies

稀释制冷机和高场螺线管系统的应用要求扫描探针显微镜技术的研究和操作的量子输运在毫开尔文温度的无序。在非常低的温度下的电子波函数的相干性可以使这种系统的传输特性对样品中的缺陷和散射中心的精确分布唯一敏感。涉及测量某些整体性质的实验（例如，作为一些外部变量（例如磁场）的函数的电导率）只能揭示关于系统中所有缺陷的净贡献的信息。相比之下，扫描探针显微镜提供了一个独特的机会，调查这些系统在单一的缺陷水平。探测和操纵小规模系统中的无序的能力，与更标准的传输探测器相结合，应该提供：1）对无序在这些系统中所起作用的理论理解的重要测试，以及2）对小金属线中的1/f噪声和电迁移等长期存在的问题的重要洞察，以及无序材料中两能级隧穿中心的性质。各种扫描探针技术的扩展，在非常低的温度下操作，也将允许空间分辨调查这样的掩埋系统，作为2维电子气在半导体异质结构，并允许新的见解运输的整数和分数量子霍尔效应制度。 在过去的十年中，凝聚态物理学的两个领域引起了人们极大的兴趣和活动：纳米尺度器件和系统中的电输运，以及用扫描隧道显微镜和相关显微镜研究表面。这些新工具在表面结构和缺陷的研究，复杂分子和磁性系统的研究以及通过操纵单原子构建块制造非常小的结构中得到了广泛的应用。 这项研究，其中稀释冰箱和高场螺线管系统的要求，旨在应用扫描探针显微镜技术的研究和操纵的量子输运在非常低的毫开尔文温度的无序。目的是探索无序对金属体电子性质影响的微观起源。

A dilution refrigerator and a high field solenoid system are requested for application of scanning probe microscopy techniques to the study and manipulation of disorder in quantum transport at millikelvin temperatures. The coherence of the electron wavefunction at very low temperatures can make the transport properties of such systems uniquely sensitive to the exact distribution of defects and scattering centers in the sample. Experiments which involve the measurement of some bulk property (e.g., conductivity) as a function of some external variable (e.g. magnetic field) can only reveal information about the net contribution of all the defects in the system. In contrast, scanned probe microscopies offer a unique opportunity to investigate these systems at the single defect level. The ability to probe and manipulate disorder in small scale systems, in combination with more standard probes of transport should provide: 1) important tests of the theoretical understanding of the role that disorder plays in these systems, and 2) signific ant insight into such long standing problems as 1/f noise and electromigration in small metal wires, and the nature of two level tunneling centers in disordered materials. The extension of a variety of scanned probe techniques to operation at very low temperatures will also allow the spatially resolved investigation of such buried systems, as the 2-dimensional electron gas in semiconductor heterostructures, and allow new insights into transport in the integer and fractional quantum Hall effect regimes. %%% Over the past decade, there has been great deal of interest and activity in two areas of condensed matter physics: electrical transport in nanometer scale devices and systems, and the study of surfaces with the scanning tunneling microscope and related microscopies. These new tools have found wide use in the study of the structure, and defects, on surfaces, study of complex molecules and magnetic systems, and fabrication of very small st ructures through the manipulation of single-atom-building blocks. This research, for which a dilution refrigerator and a high field solenoid system are requested, seeks to apply scanning probe microscopy techniques to the study and manipulation of disorder in quantum transport at very low, millikelvin temperatures. The aim is to probe the microscopic origins of the effects of disorder on the bulk electronic properties of metals.