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

为了应用扫描探针显微镜技术研究和操纵毫伏温下量子输运中的无序，需要一台稀释制冷机和一个高场螺线管系统。在很低的温度下，电子波函数的相干性可以使这类系统的输运性质对样品中缺陷和散射中心的准确分布特别敏感。涉及测量某些体物性(例如电导率)作为某些外部变量(例如磁场)的函数的实验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在单个缺陷水平上调查这些系统的独特机会。在小尺度系统中探测和操纵无序的能力，与更标准的输运探测相结合，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；2)对诸如1/f噪声和小金属线中的电迁移等长期存在的问题的重要洞察，以及无序材料中两个能级隧道中心的性质。将各种扫描探测技术扩展到在极低温度下工作，也将允许对这种埋藏系统的空间分辨研究，如半导体异质结中的二维电子气，并允许对整数和分数量子霍尔效应区域中的输运进行新的洞察。在过去的十年里，凝聚态物理在两个领域引起了极大的兴趣和活跃：纳米设备和系统中的电子输运，以及用扫描隧道显微镜和相关显微镜研究表面。这些新的工具在研究表面的结构和缺陷、研究复杂的分子和磁系统以及通过操纵单原子构建块来制造非常小的结构方面得到了广泛的应用。这项研究需要一台稀释制冷机和一个高场螺线管系统，旨在将扫描探针显微镜技术应用于研究和操纵极低温度下量子输运中的无序。其目的是探索无序对金属整体电子性质影响的微观根源。

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.