Search for a novel double honeycomb lattice superconductor

寻找新型双蜂窝晶格超导体

基本信息

批准号：
13640347
负责人：
SHAMOTO Shin-ichi
金额：
$ 2.3万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640347/
关键词：
Double honeycomb lattice Superconducting Material search HfNCl 超電導超伝道

项目摘要

We have synthesized double honeycomb lattice superconductors, such as Li_xZrNCl (T_c=15 K), Li_xNBr (T_c=13 K), and Na_xHfNCl (T_c=20-23 K) under ambient pressure. By synthesizing large amount of sample, we have succeeded to determine these structural parameters by Rietveld analysis using neutron powder diffraction data one by one. As a result, we found the close relationship between the transfer integral estimated by Harrison approximation and the superconducting transition temperature T_c in these compounds. This is partially because Na_xHfNCl has large Debye temperature in spite of the large mass of a Hf atom, I.e., stiff lattice. It basically suggests that the longer bond distance between the nearest neighbor transition metal atoms are, the higher T_c is. Based on this finding, we have selected YOCl, TaON, and CeSI as high-T_c candidates of double honeycomb lattice superconductors. Our simple estimation predicts that Na_xYOCl would have a T_c of 30 K. After we successfully sysnthesized Li_xYOCl powder sample in DRI-LAB glove box under an atmosphere of less than 1 ppm moisture, we found it was an insulator with curious temperature dependence of magnetization. This is the first discovery of a double honeycomb lattice insulator. It proves that Na_xHfNCl locates close to an insulator region in our transfer integral phase diagram. This result suggests that Li_xYOCl sample might be a high-T_c superconductor under pressure.

我们已经合成了双蜂窝晶格超导体，例如li_xzrncl（t_c = 15 K），li_xnbr（t_c = 13 k）和na_xhfncl（T_C = 20-23 K）在环境压力下。通过合成大量样品，我们成功地通过Rietveld分析使用中子粉末衍射数据来确定这些结构参数。结果，我们发现了这些化合物中Harrison近似估计的转移积分与超导过渡温度T_C之间的密切关系。这部分是因为Na_xhfncl尽管有大量的HF原子，即刚性晶格，但Na_xhfncl的温度较高。它基本上表明，最近的邻居过渡金属原子之间的较长键距离是较高的T_C。基于这一发现，我们选择了YOCL，TAON和CESI作为双蜂窝晶格超导体的高-T_C候选。我们的简单估计预测Na_xyocl将具有30 K的T_C。在我们成功地在小于1 ppm的水分的大气下，成功地在DRI-LAB杂物盒中取得了Sysnthesned Li_xyocl粉末样品后，我们发现它是一种奇特的磁化温度依赖性的绝缘子。这是双蜂窝晶格绝缘子的第一个发现。它证明Na_xhfncl在我们的传输积分相图中定位靠近绝缘体区域。该结果表明，在压力下，Li_xyocl样品可能是高T_C超导体。