Measurement of the Superfluid Density and other Electronic Properties of Electron-Doped Cuprate Superconductors

本项目主要研究电子掺杂铜酸盐中CuO(2)面的电子性质，例如Pr(2-x)Ce(X)CuO(4)和La(2-x)Ce(X)CuO(4)，并与空穴掺杂铜酸盐，特别是密切相关的化合物La(2-x)Sr(X)CuO(4)进行比较。争论的焦点是e掺杂铜酸盐中超导状态的性质，以及在最佳掺杂附近是否存在配对对称性的转变。该项目将提供两个具有根本重要性的量的第一次测量。其一是超流体密度的大小与温度的关系，它与磁穿透深度的平方成反比。在很宽的掺杂范围内，样品的穿透深度将从0.5K测量到超导转变温度。另一个是超导转变时的电子热容异常。还将进行正常态输运的辅助测量，例如，电阻率和霍尔系数。研究将为研究生和本科生提供最先进的实验技术方面的优秀培训。该项目得益于与世界领先的电子掺杂铜酸盐薄膜制造商、日本NTT的直藤道雄博士的合作。凝聚态物理和材料科学的一个核心问题是识别使电子能够在固体中运动的微观机制，而不是附着在特定原子上。本项目的重点是了解一类超导化合物中在铜氧化物平面内运动的电子，这些化合物包括Pr(2-x)Ce(X)CuO(4)和La(2-x)Ce(X)CuO(4)。自1986年发现以来，这些铜氧化物化合物的超导电性一直是国际上密集研究的主题。现在的主要问题是，这些化合物中的超导状态是否与非常类似的化合物La(2-x)Sr(X)CuO(4)中的超导状态相同。为了阐明这一问题，该项目将提供对基本重要性的量的大小和温度依赖性的测量，即超导电子的密度，以及超导电子在转变为超导状态时对热容量的贡献。这项研究将为研究生和本科生提供最先进的实验技术方面的优秀培训。

This project focuses on electronic properties of CuO(2) planes in electron-doped cuprates, e.g., Pr(2-x)Ce(x)CuO(4) and La(2-x)Ce(x)CuO(4), in comparison with hole-doped cuprates, especially the closely-related compound La(2-x)Sr(x)CuO(4). At issue is the nature of the superconducting state in e-doped cuprates, and whether there is a transition in pairing symmetry near optimal doping. The project will provide the first measurements of two quantities of fundamental importance. One is the magnitude and temperature dependence of the superfluid density, which is proportional to the inverse square of the magnetic penetration depth. The penetration depth will be measured from 0.5 K up to the superconducting transition temperature in samples spanning a wide doping range, x. Another is the electronic heat capacity anomaly at the superconducting transition. Supporting measurements of normal-state transport, e.g., resistivity and Hall coefficient will also be made. Research will provide excellent training in state-of-the-art experimental techniques to graduate and undergraduate students. This project benefits from a collaboration with the world's premier maker of electron doped cuprate films, Dr. Michio Naito of NTT, Japan.A central issue in condensed matter physics and in materials science is identification of microscopic mechanisms that enable electrons to move within a solid, rather than being attached to a particular atom. The present project focuses on understanding electrons that move within copper-oxide planes in a class of superconducting compounds that includes Pr(2-x)Ce(x)CuO(4) and La(2-x)Ce(x)CuO(4). Superconductivity in these copper-oxide compounds has been the subject of intense international research efforts since their discovery in 1986. The main question now is whether the superconducting state in these compounds is the same as found in a very similar compound, La(2-x)Sr(x)CuO(4). To illuminate this issue, the project will provide measurements of the magnitudes and temperature dependencies of quantities of fundamental importance, namely, the density of superconducting electrons, and the contribution of superconducting electrons to the heat capacity at the transition into the superconducting state. The research will provide excellent training in state-of-the-art experimental techniques to graduate and undergraduate students.