Development and Application of Layer Structured Nitride Superconductors

层状结构氮化物超导体的开发与应用

基本信息

批准号：
14350461
负责人：
YAMANAKA Shoji
金额：
$ 9.6万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

We have reported that layer structured nitride halides β-MNX (M = Zr, Hf ; X = Cl, Br, I) electron-doped by intercalation of alkali metals became superconductors. In particular, the compound cointercalated with Li and THF (tetrahydrofuran), Lio_<48>(THF)_yHfNCl, showed a high critical temperature of Tc = 25.5 K. In this study, we have collaborated with solid state physicists to investigate the superconducting mechanism, and new types of layer structured nitrides have been developed. The main results obtained are the followings;1. Single crystals of β-MNX were successfully prepared using ammonium halides as fluxes under high-pressure conditions, and their structures were determined by the single crystal X-ray analysis.2. A new electron-doping method was developed by partial deintercalation of chlorine atoms to form β-ZrNCl_<1-x> and β-HfNCl_<1-x>, which were stable in air for pretty long time. The deintercalated samples showed similar superconductivity with those electron doped by alkali metal intercalation.3. Isotope substituted β-Hf^<15>NCl was prepared, and its superconductors were derived by electron doping.4. ^<15>N NMR study revealed that the layer structured nitride superconductors were two-dimensional ones with very low carrier densities and weak phonon enhancement. The mechanism of the new superconductors cannot be interpreted in the conventional BCS theory.5. The superconducting gap was successfully measured by a break-junction method.6. Layer structured Sr_2N oriented films were prepared by MBE method in a high vacuum chamber with a nitrogen radical source.

我们报道了通过插入碱金属进行电子掺杂的层状氮化物卤化物β-MNX（M = Zr，Hf；X = Cl，Br，I）成为超导体，特别是与Li和THF（四氢呋喃）共插的化合物。，Lio_<48>(THF)_yHfNCl，显示出 Tc = 25.5 K 的高临界温度。在这项研究中，我们与固态物理学家合作研究超导机理，开发出新型层状结构氮化物，取得的主要成果如下： 1．通过单晶X射线分析确定了它们的结构。 2．开发了一种新的氯原子部分脱嵌电子掺杂方法。 β-ZrNCl_<1-x>和β-HfNCl_<1-x>在空气中稳定存在较长时间，脱嵌后的样品表现出与碱金属掺杂的β-Hf相似的超导性。3． ^<15>NCl的制备及其超导体的电子掺杂研究表明^<15>N NMR研究揭示了层状结构的氮化物。超导体是二维超导体，具有非常低的载流子密度和弱声子增强，其机理无法用传统的BCS理论来解释。5．通过断结层结构方法成功测量了超导带隙。采用MBE法在高真空室中用氮自由基源制备了Sr_2N取向薄膜。