论文标题
A15 NB $ _3 $ SI-一个“高” TC超导体合成，应在一个兆巴的压力下且在环境条件下稳态
A15 Nb$_3$Si -- A "high" Tc superconductor synthesized at a pressure of one megabar and metastable at ambient conditions
论文作者
论文摘要
到目前为止，A15 NB $ _3 $ SI是在高压（〜110 GPA）下生产的唯一高温超导体，该高温已成功地将其带回了在可稳定条件下的房间压力条件。基于目前试图创建在高压下生产的室内压力的高温超导体的极大兴趣，我们将爆炸性压缩的A15 NB $ _3 $ SI及其产量从四方NB $ _3 $ _3 $ si进行了生产。首先，在爆炸性压缩的A15 nb $ _3 $ _3 $ si材料上进行了高达88 GPA的钻石砧细胞压力测量，以跟踪TC作为压力的函数。在88 GPA时，TC被抑制至〜5.2 k。然后，使用这些TC（p）数据的A15 NB $ _3 $ SI，在室温下（在5 K时在5 K时增加到120 GPA）的压力最高为92 GPA，在Tetragonal nb $ _3 $ _3 $ si上施加了压力。电阻率的测量结果没有任何A15结构产生的迹象，即没有迹象表明A15 NB $ _3 $ SI的超导性特征。这与四方NB $ _3 $ si的爆炸性压缩（高达110 GPA）相反，后者在1981年的洛斯阿拉莫斯国家实验室实验中产生了50-70％的A15材料，TC = 18 K。 Our theoretical calculations show that A15 Nb$_3$Si has an enthalpy vs the tetragonal structure that is 0.07 eV/atom smaller at 100 GPa, implying that the accompanying high temperature (1000 deg C) caused by explosive compression is necessary to successfully drive the reaction kinetics of the tetragonal -> A15 Nb$_3$Si structural transformation. A15上的爆炸性压缩材料的退火实验达到39年的时间尺度与此观点一致。
A15 Nb$_3$Si is, until now, the only high temperature superconductor produced at high pressure (~110 GPa) that has been successfully brought back to room pressure conditions in a metastable condition. Based on the current great interest in trying to create metastable-at-room-pressure high temperature superconductors produced at high pressure, we have restudied explosively compressed A15 Nb$_3$Si and its production from tetragonal Nb$_3$Si. First, diamond anvil cell pressure measurements up to 88 GPa were performed on explosively compressed A15 Nb$_3$Si material to trace Tc as a function of pressure. Tc is suppressed to ~ 5.2 K at 88 GPa. Then, using these Tc (P) data for A15 Nb$_3$Si, pressures up to 92 GPa were applied at room temperature (which increased to 120 GPa at 5 K) on tetragonal Nb$_3$Si. Measurements of the resistivity gave no indication of any A15 structure production, i.e., no indications of the superconductivity characteristic of A15 Nb$_3$Si. This is in contrast to the explosive compression (up to P~110 GPa) of tetragonal Nb$_3$Si, which produced 50-70% A15 material, Tc = 18 K at ambient pressure, in a 1981 Los Alamos National Laboratory experiment. Our theoretical calculations show that A15 Nb$_3$Si has an enthalpy vs the tetragonal structure that is 0.07 eV/atom smaller at 100 GPa, implying that the accompanying high temperature (1000 deg C) caused by explosive compression is necessary to successfully drive the reaction kinetics of the tetragonal -> A15 Nb$_3$Si structural transformation. Annealing experiments on the A15 explosively compressed material reaching time scales of 39 years are consistent with this viewpoint.
