AI 中文总结
本研究揭示变磁体α-MnTe的巨大反常霍尔电导率源于受对称性保护的节点线，且节点线与反常霍尔电导率可通过自旋倾斜实现磁调控，明确了其变磁体贡献占主导的特性。
AI 中文摘要
变磁体α-MnTe具有高达室温的巨大反常霍尔电导率（AHC），以及由自旋和轨道极化产生的弱铁磁性。我们通过识别价带中两组不同的、受对称性强制的节点线，阐明了AHC大值的起源：这两组节点线具有Mn特征，分别位于k_z=0和k_z=π/c处，分别由镜面对称性M_z和滑移对称性G_z = {M_z | 0,0,c/2}保护。两组节点线均与能量相关，具有近似的C₆对称性，由于奈尔矢量的存在，该对称性降低为精确的C₂对称性。最高对价带呈现墨西哥帽色散，而第二高价带呈现倒置墨西哥帽色散，节点线位于两带的交叉处。在第一性原理精度范围内，我们证明这些节点线产生了实验观测到的大AHC，并与弱铁磁性存在强相互作用。我们进一步表明，即使是小的自旋倾斜也会强烈改变节点线和AHC，使它们均具有磁可调性。通过区分AHC的变磁体和铁磁体贡献，变磁体贡献在小倾斜角时占主导，而铁磁体贡献在较大倾斜角时变得显著。我们利用角分辨光电子能谱中的线性二色性，展示了布里渊区边界处节点线的特征。
英文摘要
Altermagnetic $α$-MnTe exhibits huge anomalous Hall conductivity (AHC) up to room-temperature together with weak ferromagnetism arising from spin and orbital polarizations. We clarify the origin of the large value of the AHC by identifying two sets of distinct symmetry-enforced nodal lines in the valence bands with Mn character, located at $k_z=0$ and $k_z=\fracπ{c}$, protected by mirror symmetry $M_z$ and glide symmetry $G_z = \{M_z\,|\,0,0,\tfrac{c}{2}\}$, respectively. Both nodal lines are energy-dependent with an approximate C$_6$ symmetry, which is reduced to an exact C$_2$ symmetry due to the presence of the Néel vector. The highest valence band exhibits a Mexican-hat dispersion, whereas the second-highest valence band exhibits an inverted Mexican-hat dispersion, with nodal lines at the crossing between the two bands. Within first-principles accuracy, we demonstrate that these nodal lines give rise to the large AHC observed experimentally and exhibit a strong interplay with the weak ferromagnetism. We further show that even a small spin canting strongly modifies the nodal lines and the AHC, making them both magnetically tunable. By disentangling the altermagnetic and ferromagnetic contributions to the AHC, the altermagnetic contribution dominates at small canting angles, while the ferromagnetic contribution becomes sizeable for larger values. Using linear dichroism in angle-resolved photoemission spectroscopy, we show a signature of the nodal line at the border of the Brillouin zone.
