High critical field superconductivity at ambient pressure in MoB2 stabilized in the P6/mmm structure via Nb substitution
High critical field superconductivity at ambient pressure in MoB2 stabilized in the P6/mmm structure via Nb substitution
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DOI：
10.1103/physrevb.106.174515
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发表时间：
2022-11
影响因子：
3.7
通讯作者：
A. Hire;S. Sinha;J. Lim;J. Kim;P. Dee;L. Fanfarillo;J. Hamlin;R. Hennig;P. Hirschfeld;G. Stewart
中科院分区：
文献类型：
--
作者：
A. Hire;S. Sinha;J. Lim;J. Kim;P. Dee;L. Fanfarillo;J. Hamlin;R. Hennig;P. Hirschfeld;G. Stewart
最近发现，在高压下，MoB_2在临界温度T_c高达32 K时具有超导电性。超导电性的发展似乎遵循压力诱导的结构转变，从环境压力R$\bar{3}$m结构到MgB$_2$-like P6/mmm结构。这表明，显着高$T_c$值之间的二硼化物并不局限于MgB$_2$以前似乎是这样的情况下，类似的高$T_c$值可能会出现在其他二硼化物，如果他们可以强制到MgB$_2$结构。在本文中，我们表明，密度泛函理论计算表明，声子自由能稳定的P6/mmm结构的R$\bar{3}$m在高温下在整个Nb$_{1-x}$Mo $_x$B$_2 $系列。X射线衍射分析表明，所合成的Nb取代MoB_2 $具有MgB_2 $晶体结构。高磁场电阻率测量和比热测量表明，Nb${1-x}$Mo $xB $2 $具有超导性，其T_c高达8 K，临界磁场接近6 T。
Recently it was discovered that, under elevated pressures, MoB$_2$ exhibits superconductivity at a critical temperature, $T_c$, as high as 32 K. The superconductivity appears to develop following a pressure-induced structural transition from the ambient pressure R$\bar{3}$m structure to an MgB$_2$-like P6/mmm structure. This suggests that remarkably high $T_c$ values among diborides are not restricted to MgB$_2$ as previously appeared to be the case, and that similarly high $T_c$ values may occur in other diborides if they can be coerced into the MgB$_2$ structure. In this paper, we show that density functional theory calculations indicate that phonon free energy stabilizes the P6/mmm structure over the R$\bar{3}$m at high temperatures across the Nb$_{1-x}$Mo$_x$B$_2$ series. X-ray diffraction confirms that the synthesized Nb-substituted MoB$_2$ adopts the MgB$_2$ crystal structure. High magnetic field electrical resistivity measurements and specific heat measurements demonstrate that Nb$_{1-x}$Mo$_x$B$_2$ exhibits superconductivity with $T_c$ as high as 8 K and critical fields approaching 6 T.