In a kagome lattice, the time reversal symmetry can be broken by a staggered magnetic flux emerging from ferromagnetic ordering and intrinsic spin-orbit coupling, leading to several wellseparated nontrivial Chern bands and intrinsic quantum anomalous Hall effect. Based on this idea and ab initio calculations, we propose the realization of the intrinsic quantum anomalous Hall effect in the single layer Cs2Mn3F12 kagome lattice and on the (001) surface of a Cs2LiMn3F12 single crystal by modifying the carrier coverage on it, where the band gap is around 20 meV. Moreover, a simplified tight binding model based on the in-plane ddσantibonding states is constructed to understand the topological band structures of the system.
The macroscopic signature for Weyl nodes so far has been the negative longitudinal magnetoresistance arising from the chiral anomaly. However, negative longitudinal magnetoresistance is not unique to chiral anomaly and can arise due to completely different mechanisms such as current jetting or in ferromagnetic systems due to the suppression of scattering with magnons. Therefore, a macroscopic effect that can be uniquely attributed to the presence of Weyl nodes is desirable. Here we show that the planar Hall effect could be a hallmark for Weyl nodes. We investigated the anisotropic magnetoresis…
Robust magnetotransport in disordered ferromagnetic kagome layers with quantum anomalous Hall effect
对无序铁磁可果美层的磁输运性质进行了数值研究。我们发现在可果美层状材料（如Fe $_3$ Sn $_2$，Co $_3$ Sn $_2$ S $_2$，和Mn $_3$ Sn）中可以实现大的畴壁磁电阻或负磁电阻，表现出量子反常霍尔效应.戈薇层表现出强烈的磁各向异性和大的磁阻取决于它们的磁织构。这些畴壁磁阻预计将是强大的，对无序和观察无关的畴壁厚度，在铁磁金属中的常规畴壁磁阻。
Magnetic Weyl semimetals (mWSMs) are characterized by linearly dispersive bands with chiral Weyl node pairs associated with broken time reversal symmetry. One of the hallmarks of mWSMs is the emergence of large intrinsic anomalous Hall effect. On heating the mWSM above its Curie temperature, the magnetism vanishes while exchange-split Weyl point pairs collapse into doubly-degenerated gapped Dirac states. Here, we reveal the attractive potential of these Dirac nodes in paramagnetic state for efficient spin current generation at room temperature via the spin Hall effect. Ni and In are introduced…
Recently, kagome materials have become an engrossing platform to study the interplay among symmetry, magnetism, topology, and electron correlation. The latest works on RMn6Sn6 (R = rare earth metal) compounds have illustrated that this family could be intriguing to investigate various physical phenomena due to large spin-orbit coupling and strong magnetic ordering. However, combined transport and spectroscopic studies in RMn6Sn6 materials are still limited. Here, we report magnetic, magneto-transport, and angle-resolved photoemission spectroscopy measurements of a kagome magnet ErMn6Sn6 that u…
The topological kagome magnet (TKM) Fe3Sn2 exhibits unusual topological properties, flat electronic bands, and chiral spin textures, making it an exquisite materials platform to explore the interplay between topological band structure, strong electron correlations, and magnetism. Here we report the first synthesis of high-quality epitaxial (0001) Fe3Sn2 films with large intrinsic anomalous Hall effect close to that measured in bulk single crystals. In addition, we measured a large, anisotropic anomalous Nernst coefficient Syx of 1.26 μV/K, roughly 2-5x greater than that of common ferromagnets,…
The two dimensional kagome spin lattice structure of Mn atoms in the family of Mn$_3$X non-collinear antiferromagnets are providing substantial excitement in the exploration of Berry curvature physics and the associated non-trivial magnetotransport responses. Much of these studies are performed in the hexagonal systems, mainly Mn$_3$Sn and Mn$_3$Ge, with the kagome planes having their normal along the [001] direction. In this manuscript, we report our study in the cubic Mn$_3$Pt thin films with their kagome planes normal to the [111] crystal axis. Our studies reveal a hole conduction dominant …
Owing to its charge-free property, magnon is highly promising to achieve dissipationless transport without Joule heating and thus potentially applicable to energy-efficient devices. Moreover, a kagome lattice, as stacking layers of many magnon ferromagnets, also exhibits valley structure in quasiparticle spectra, which are likely to add a new dimension to magnon excitation. Here, we investigate valley magnon and associated valley modulation in a kagome lattice, with staggered exchange interaction and Dzyaloshinskii-Moriya interaction. The staggered exchange interaction breaks spatial inversion…
The charge-density wave (CDW) phase is often accompanied by the condensation of a soft acoustic phonon mode, giving rise to lattice distortion and charge density modulation. This picture was challenged for the recently discovered kagome metal CsV$_3$Sb$_5$, based on the evidence of absence of soft phonons. Here we report the observation of Raman-active CDW amplitude modes in this material, which are collective excitations typically thought to emerge out of frozen soft phonons. The amplitude modes strongly hybridize with other superlattice modes, imparting them with clear temperature-dependent …
Probing the anomalous symmetry-breaking in kagome material CsV3Sb5 via third-order nonlinearity
National Laboratory of Solid-State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Jiangsu Physical Science Research Center, and School of Physics, Nanjing University（南京大学固体微结构物理国家重点实验室、先进微结构协同创新中心、江苏物理科学研究中心和物理学院）；Institute of Atom Manufacturing, Nanjing University（南京大学原子制造研究所）；Jiangsu Provincial Key Laboratory of Atomic Level Manufacturing, Nanjing Institute of Atomic Scale Manufacturing（江苏省原子级制造重点实验室、南京原子尺度制造研究所）；School of Physics and Electronic Information, Jiangsu Second Normal University（江苏第二师范学院物理与电子信息学院）
Anomalous Hall Effect in $t_{2g}$ Orbital Kagome Lattice due to Non-collinearity:Significance of Orbital Aharonov-Bohm Effect
通过引入d轨道自由度，提出了倾斜铁磁金属中自旋结构驱动反常霍尔效应（AHE）的新机制。我们发现，在非共线自旋结构和自旋轨道相互作用的存在下，传导电子由于复杂的d轨道波函数而获得Berry相。由这种轨道导出的Berry相驱动的AHE比由自旋手征诱导的AHE大得多，这自然解释了烧绿石Nd $_2$ Mo $_2$ O $_7$中自旋结构驱动的AHE的显著特征。由于所提出的AHE甚至可以发生在共面自旋序（$M_z=0$），它有望出现在其他有趣的几何挫折系统。
The possibility of dissipationless chiral edge states without the need of an external magnetic field in the quantum anomalous Hall effect (QAHE) offers a great potential in electronic/spintronic applications. The biggest hurdle for the realization of a room-temperature magnetic Chern insulator is to find a structurally stable material with a sufficiently large energy gap and Curie temperature that can be easily implemented in electronic devices. This work based on first-principle methods shows that a single atomic layer of V2O3 with honeycomb-kagome (HK) lattice is structurally stable with a s…
最近发现的材料Co $_3$ Sn $_2$ S $_2$表现出令人印象深刻的量子反常霍尔（QAH）导电性行为，其由$z$方向上的铁磁性和$xy$平面上的反铁磁性之间的相互作用驱动。基于这些事实，我们首先建立并研究了一个自旋为1/2的模型来描述Kagome平面上Co原子的磁性。然后，我们包括传导电子耦合到自旋-1/2通过一个强大的洪德耦合。自旋-轨道耦合导致拓扑低能带。对于2/3的在位占有率，我们发现从QAH铁磁绝缘相与陈数1的量子自旋霍尔（QSH）反铁磁相的拓扑转变。QAH阶段是金属时，稍微改变现场占用。考虑到温度的影响，我们包括波动方向的洪德耦合。我们展示了如何霍尔电导率现在可以顺利地发展时，自旋开发的$120^o$反铁磁性的$xy$平面，并可以同步与铁磁分数。
The anomalous Hall effect, a hallmark of broken time-reversal symmetry and spin-orbit coupling, is frequently observed in magnetically polarized systems. Its realization in non-magnetic systems, however, remains elusive. Here, we report on the observation of anomalous Hall effect in nominally non-magnetic KTaO3. Anomalous Hall effect emerges in reduced KTaO3 and shows an extrinsic to intrinsic crossover. A paramagnetic behavior is observed in reduced samples using first principles calculations and quantitative magnetometry. The observed anomalous Hall effect follows the oxygen vacancy-induced …
