Atomic Resolution Dual-Point Superconducting Phase STM

非技术：该奖项来自材料研究部凝聚态物理项目，支持开发和证明新型相敏超导双尖扫描隧道显微镜(STM)产生新型原子分辨率图像的可行性。自1981年发明以来，扫描隧道显微镜(STM)通过提供精确到原子尺度的固体的图像和详细的电子信息，彻底改变了人们对材料物理的理解。扫描隧道显微镜通过测量电子在样品表面和非常尖锐的尖端之间穿行的电流来产生图像，尖端在样品表面上方非常近地扫描。隧穿是一种量子力学过程，它允许电子流经经典物理定律禁止它们进入的区域。正在开发的新型扫描隧道显微镜使用由超导导线连接的两个超导尖端；它的工作温度比绝对零度高出几分之一度，并允许相干库珀对隧道成像。该项目完成后，将用于研究传统超导体以及表现出奇异超导形式的新材料中原子尺度的超导电性。用双针尖超导STM进行的测量可以用来探索引起超导的潜在机制。该项目涉及本科生、研究生和博士后。材料研究部凝聚态物理项目颁发的这一奖项支持开发一种新型的相敏超导双尖扫描隧道显微镜(STM)，并使用该仪器生成新颖的原子分辨率图像，获得对高温超导(TC)超导产生机制和其他材料中有趣现象的新见解。该系统基于现有的毫微电子扫描隧道显微镜的改进，其中两个尖端可以独立扫描，可以是正常的或超导的，允许准粒子隧道或量子相位涨落极限的库珀对隧道。通过在两个超导尖端之间增加超导导线连接，并使用超导样品，与样品形成超导量子干涉装置(SQUID)回路。通过对针尖进行适当的偏置，这可以减少纳米针尖上的规范不变相位差的波动，从而实现通量和相敏成像。特别是，这一新能力将允许在原子尺度上成像超导样品表面规范不变相位差的空间相关性。该显微镜将在35mK下对Nb和Al等众所周知的超导材料进行测试，并生成涡旋核心附近的局域规范不变相位差、原子缺陷、台阶和其他表面不规则性的图像。该项目涉及本科生和研究生以及博士后。

Non-Technical:This award from the Condensed Matter Physics Program of the Division of Materials Research supports the development and proof of feasibility of a novel phase-sensitive superconducting dual-tip scanning tunneling microscope (STM) to generate novel atomic-resolution images. Since their invention in 1981, scanning-tunneling microscopes (STMs) have revolutionized the understanding of the physics of materials by providing images and detailed electronic information of solids down to the atomic scale. An STM creates an image by measuring the current from electrons that tunnel between a sample surface and an extremely sharp tip that is scanned very closely above the sample surface. Tunneling is a quantum-mechanical process that allows electrons to flow through regions that they are forbidden from entering by the laws of classical physics. The novel type of STM being developped uses two superconducting tips connected by a superconducting wire; it operates a fraction of a degree above absolute zero temperature, and allows the imaging of coherent Cooper pair tunneling. This project, when completed, will be used to study superconductivity at the atomic scale in conventional superconductors as well as newer materials which display exotic forms of superconductivity. Measurements made with a dual-tip superconducting STM can be used to probe the underlying mechanisms causing superconductivity. The project involves undergraduate and graduate students as well as postdocs.Technical AbstractThis award from the Condensed Matter Physics Program of the Division of Materials Research supports the development of a novel phase-sensitive superconducting dual-tip scanning tunneling microscope (STM) and the use of the instrument to generate novel atomic-resolution images and gain new insight into the mechanism producing superconductivity in high-transition temperature (Tc) superconductors and interesting phenomena in other materials. The system is based on a modification of an existing millikelvin STM in which two tips can be independently scanned, and can be either normal or superconducting, allowing for quasi-particle tunneling, or Cooper-pair tunneling in the quantum phase-fluctuation limit. By adding a superconducting wire connection between two superconducting tips, and using a superconducting sample, a Superconducting Quantum Interference Device (SQUID) loop is formed with the sample. With suitable biasing of the tips, this reduces fluctuations in the gauge-invariant phase difference across the nano-scale tips, allowing flux and phase sensitive imaging. In particular, this new capability will allow imaging of the spatial dependence of the gauge-invariant phase difference on the surface of superconducting samples at the atomic scale. The microscope will be tested at 35mK on well-understood superconducting materials such as Nb and Al and images generated of spatial variations in the local gauge-invariant phase difference near vortex cores, atomic defects, steps, and other surface irregularities. The project involves undergraduate and graduate students as well as postdocs.