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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.

我们报道了层状结构氮卤化物β-MNX （M = Zr, Hf; X = Cl, Br， I）掺杂碱金属后成为超导体。其中Li和THF（四氢呋喃）共插的化合物Lio_<48>(THF)_yHfNCl的临界温度为Tc = 25.5 K。在这项研究中，我们与固体物理学家合作研究了超导机制，并开发了新型层状结构氮化物。主要研究结果如下：1。以卤化铵为助熔剂，在高压条件下成功制备了β-MNX单晶，并通过x射线单晶分析确定了β-MNX的结构。采用氯原子部分脱插的方法制备了β-ZrNCl_<1-x>和β-HfNCl_<1-x>，两者在空气中稳定时间较长。脱嵌电子的超导性与碱金属嵌入电子的超导性相似。制备了同位素取代β-Hf^<15>NCl，并通过电子掺杂得到了其超导体。^<15>N核磁共振研究表明，层状结构氮化物超导体为二维超导体，载流子密度极低，声子增强弱。新超导体的机理不能用传统的BCS理论来解释。用断结法成功地测量了超导间隙。在氮自由基源的高真空室中，采用MBE法制备了层状结构的Sr_2N取向薄膜。