轨道阻挫的Ba$_2$MgReO$_6$中位点间库仑排斥驱动的四极不稳定性与磁有序
Intersite Coulomb repulsion driven quadrupole instability and magnetic ordering in the orbital frustrated Ba$_2$MgReO$_6$
AI总结：
本文通过自洽Hartree-Fock方法研究Ba$_2$MgReO$_6$，发现位点间库仑排斥$V$和易平面各向异性可消除轨道阻挫，反平行四极矩诱导倾斜反铁磁态并首次发现多种八极矩。
摘要：
我们发展了一种无限制Hartree-Fock平均场方法，自洽地包含库仑排斥$U$、$V$和自旋-轨道耦合$λ$，以研究Ba$_2$MgReO$_6$中结构不稳定性和磁有序的机制。计算了在$λ$=0.28eV时随$U$和$V$变化的完整四极相图。我们的结果表明，必须考虑易平面各向异性和位点间库仑排斥$V$才能消除轨道阻挫。当$V$增大到$>$20meV时，会使四极矩$Q_{x^2-y^2}$反平行排列，并伴随小的平行$Q_{3z^2-r^2}$，从而使Ba$_2$MgReO$_6$稳定在体心四方结构中。这种反平行的$Q_{x^2-y^2}$提供了一种新的Dzyaloshinskii-Moriya相互作用机制，并导致沿[110]轴的倾斜反铁磁（CAF）态。此外，在CAF态中首次发现了可观的八极矩，如$O_{21}^{31}$、$O_{21}^{33}$、$O_{21}^{34}$和$O_{21}^{36}$。我们的研究不仅为Ba$_2$MgReO$_6$的实验结果提供了全面的理解，还揭示了5d化合物的一些共性。
英文摘要：
We develop an unrestricted Hartree-Fock mean-field method including Coulomb repulsion $U$, $V$ and spin-orbital coupling $λ$ self-consistently to investigate the mechanism of structural instability and magnetic ordering in Ba$_2$MgReO$_6$. A comprehensive quadrupole phase diagram versus $U$ and $V$ with $λ$=0.28eV is calculated. Our results demonstrate that the easy-plane anisotropy and the intersite Coulomb repulsion $V$ must be considered to remove the orbital frustration. The increasing of $V$ to $>$20meV would arrange quadrupole $Q_{x^2-y^2}$ antiparallelly, accompanied with small parallel $Q_{3z^2-r^2}$, and stabilize Ba$_2$MgReO$_6$ into the body-centered tetragonal structure. Such antiparallel $Q_{x^2-y^2}$ provides a new mechanism of Dzyaloshinskii-Moriya interaction, and gives rise to the canted antiferromagnetic (CAF) state along [110] axis. Moreover, sizable octupoles such as $O_{21}^{31}$, $O_{21}^{33}$, $O_{21}^{34}$ and $O_{21}^{36}$ are discovered for the first time in CAF state. Our study not only provides a comprehensive understanding of the experiment results in Ba$_2$MgReO$_6$, but also reveals some commonalities of 5d compounds.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
