论文标题
Bafe $ _2 $ SE $ _3 $的太空集团对称
Space Group Symmetry of BaFe$_2$Se$_3$: ab initio-Experiment Phonon Study
论文作者
论文摘要
本文介绍了Bafe $ _2 $ SE $ _3 $的结构动力学的研究。我们结合了第一原则计算，红外测量和彻底的对称分析。我们的研究证实，即使在室温下，$ PNMA $也不能是Bafe $ _2 $ SE $ _3 $的空间组。声子分配需要$ pm $才能为Bafe $ _2 $ SE $ _3 $太空集团，不仅在磁性阶段，而且在室温下的顺磁性阶段。这是由于沿梯子的短距离旋转阶之间的强距离以及与Fe-Fe键长相关的晶格自由度。这种耦合导致键长的模式从交替的梯形链球菌（如$ pnma $）变为交替的小/大矩形。在这两种模式中，只有后者与观察到的块型磁性结构完全兼容。最后，我们建议对0-600 \，k范围的BAFE $ _2 $ SE $ _3 $相位图进行完整的对称分析。
This paper presents a study of the structure dynamics in BaFe$_2$Se$_3$. We combined first-principle calculations, infrared measurements and a thorough symmetry analysis. Our study confirms that $Pnma$ cannot be the space group of BaFe$_2$Se$_3$, even at room temperature. The phonons assignment requires $Pm$ to be the BaFe$_2$Se$_3$ space group, not only in the magnetic phase, but also in the paramagnetic phase at room temperature. This is due to a strong coupling between a short range spin-order along the ladders, and the lattice degrees of freedom associated with the Fe-Fe bond length. This coupling induces a change in the bond-length pattern from an alternated trapezoidal one (as in $Pnma$) to an alternated small/large rectangular one. Out of the two patterns, only the latter is fully compatible with the observed block-type magnetic structure. Finally, we propose a complete symmetry analysis of the BaFe$_2$Se$_3$ phase diagram in the 0-600\,K range.
