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Superconductivity in water intercalated Na CoO2 thin films

水插层 Na CoO2 薄膜的超导性

基本信息

批准号：
20845042
负责人：
Professor Dr. Lambert Alff
金额：
--
依托单位：
Max-Planck-Institut für Festkörperforschung (MPI-FKF)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2006
资助国家：
德国
起止时间：
2005-12-31 至 2009-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/20845042?language=en
关键词：
Superconductivity water intercalated Na CoO2

项目摘要

Sodium cobaltate is a material with a large variety of interesting properties that originate in strong electron correlation effects. While its large Seebeck coefficient and low resistivity makes it a candidate for thermoelectric device applications, the layered sodium cobalt oxyhydrate NaxCo02 ¿ yH2O (x < 0.35, y < 1.3) has recently been shown to be superconducting with TC w 4.5K. The phase diagram of this superconductor with a triangular cobalt-oxygen lattice resembles that of the high-temperature superconductors (HTSC) with square copper-oxygen layers. The study of this new material has thus far been restricted to single crystals or poly crystalline ceramic materials. Only very recently, the first thin films of sodium cobaltate have been successfully prepared. The work proposed here will take advantage of the unique opportunities offered by the synthesis of high-quality thin films. The phase purity and surface quality of epitaxial thin films grown by pulsed laser deposition (PLD) are far superior to those of ceramic samples. High-quality films can be fabricated over a wider range of Na concentrations than single crystals. This will enable a comprehensive characterization of the optical properties by infrared and Raman scattering experiments over the entire phase diagram. Moreover, water-intercalated superconducting thin films have recently been prepared by the applicants, opening up the tantalizing possibility of carrying out phase-sensitive Josephson interference experiments to determine the pairing symmetry, as well as a search for pseudogap phenomena well known from HTSC. Altogether, these studies will provide deepened insight into a new superconducting system where coupled spin and charge dynamics are expected to play an essential role for superconductivity.

钴酸钠是一种具有多种有趣性质的材料，这些性质源于强电子相关效应。虽然其大的塞贝克系数和低电阻率使其成为热电器件应用的候选者，但层状钠钴氧水合物NaxCo 02 <$yH2O（x < 0.35，y < 1.3）最近已被证明是超导的，TC w 4.5K。这种具有三角形钴氧晶格的超导体的相图类似于具有正方形铜氧层的高温超导体（HTSC）的相图。这种新材料的研究迄今为止仅限于单晶或多晶陶瓷材料。直到最近，才成功地制备了第一批钴酸钠薄膜。这里提出的工作将利用高质量薄膜合成所提供的独特机会。脉冲激光沉积（PLD）外延薄膜的相纯度和表面质量远上级陶瓷样品。高质量的薄膜可以在比单晶更宽的Na浓度范围内制造。这将使一个全面的表征的光学性能的红外和拉曼散射实验在整个相图。此外，水插层超导薄膜最近已经由申请人制备，打开了诱人的可能性，进行相敏约瑟夫森干涉实验，以确定配对对称性，以及从HTSC众所周知的赝能隙现象的搜索。总之，这些研究将提供深入了解一个新的超导系统，耦合自旋和电荷动力学预计将发挥重要作用的超导性。