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arXiv 2408.02504cond-mat.str-el
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探索 MgMn$_6$Sn$_6$ 中的磁性和拓扑复杂性:从阻挫基态到非平庸霍尔电导率

Exploring magnetic and topological complexity in MgMn$_6$Sn$_6$: from frustrated ground states to nontrivial Hall conductivity

Jyotirmoy Sau, Hrishit Banerjee, Sourabh Saha, Nitesh Kumar, Manoranjan Kumar

AI总结:

该研究结合 DFT 与 DMFT 计算,揭示 MgMn$_6$Sn$_6$ 的阻挫磁性基态、SOC 打开的拓扑能隙及其显著自旋霍尔电导率。

摘要:

我们探索了引人关注的拓扑巡游磁体 MgMn$_6$Sn$_6$,其特征是包裹一个六方 Sn 层的双层 kagome Mn 层。利用从头算密度泛函理论和动力学平均场理论计算,我们揭示了其磁性基态的复杂电子性质和多体构型。Mn d 轨道电子形成具有显著量子涨落的阻挫多体基态,导致相互竞争的反铁磁和铁磁自旋交换。我们的能带色散计算揭示了 k$_z$ = 0 平面中一条受镜面对称性保护的节点线。当引入自旋轨道耦合(SOC)时,由于磁有序破坏时间反演对称性,沿节点线形成的能隙被解除,从而产生显著的内禀 Berry 曲率。我们在费米能级(E$_F$)附近识别出 Dirac 费米子、van Hove 奇点和平带,SOC 在关键点引入有限能隙。平带与 E$_F$ 的独特邻近性表明存在潜在不稳定性。自旋轨道耦合在 Dirac 带与平带之间的二次接触点打开 20 meV 的能隙,赋予非零 Z$_2$ 不变量。这导致显著的自旋霍尔电导率。尽管电子相互作用产生了较大的非相干散射,能带交叉和平带特征在有限温度下仍然存在。MgMn$_6$Sn$_6$ 展现出引人关注的拓扑和磁性,并在自旋电子学中具有良好应用前景。

英文摘要:

We explore the intriguing topological itinerant magnet MgMn$_6$Sn$_6$, characterized by bilayer kagome Mn layers encasing a hexagonal Sn layer. Using \textit{ab initio} Density functional theory and Dynamical mean-field theory calculations, we uncover the complex electronic properties and many-body configuration of its magnetic ground state. Mn d-orbital electrons form a frustrated many-body ground state with significant quantum fluctuations, resulting in competing antiferromagnetic and ferromagnetic spin exchanges. Our band dispersion calculations reveal a mirror symmetry-protected nodal line in the \textit{k}$_z$ = 0 plane. When spin-orbit coupling (SOC) is introduced, the gap is formed along the nodal line lifted due to broken time-reversal symmetry with magnetic ordering, leading to substantial intrinsic Berry curvature. We identify Dirac fermions, van Hove singularities, and flat band near the Fermi energy (\textit{E}$_F$), with SOC introducing a finite gap at key points. The unique proximity of the flat band to \textit{E}$_F$ suggests potential instabilities. Spin-orbit coupling opens a 20 meV gap at the quadratic touching point between the Dirac and flat band, bestowing a nonzero Z$_2$ invariant. This leads to a significant spin Hall conductivity. Despite the presence of large incoherent scattering due to electronic interactions, band crossings and flat band features persist at finite temperatures. MgMn$_6$Sn$_6$ exhibits intriguing topological and magnetic properties, with promising applications in spintronics.

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