We systematically investigate the influence of high pressure on the electronic transport properties of layered ferromagnetic materials, in particular, those of Fe3GeTe2. Its crystal sustains a hexagonal phase under high pressures up to 25.9 GPa, while the Curie temperature decreases monotonously with the increasing pressure. By applying appropriate pressures, the experimentally measured anomalous Hall conductivity, σ A xy , can be efficiently controlled. Our theoretical study reveals that this finding can be attributed to the shift of the spin-orbit-coupling-induced splitting bands of Fe atoms. With loading compression, σ A xy reaches its maximal value when the Fermi level lies inside the splitting bands and then attenuates when the splitting bands float above the Fermi level. Further compression leads to a prominent suppression of the magnetic moment, which is another physical cause of the decrease in σ A xy at high pressure. These results indicate that the application of pressure is an effective approach in controlling the anomalous Hall conductivity of layered magnetic materials, which elucidates the physical mechanism of the large intrinsic anomalous Hall effect.Introduction-. Anomalous Hall effect has been one of the most attractive but unsolved topics within the condensed matter community ever since its experimental discovery [1]. In general, anomalous Hall effect is closely related to the material magnetization, and its fundamental origin in different materials is debatable: it is commonly rationalized as being extrinsic disorder-induced effects (e.g., skew-scattering and side jump) or intrinsic Berry-phase effect [2][3][4][5][6][7]. Nevertheless, new types of anomalous Hall effects in material systems besides those in ferromagnetic materials (i.e., topological Hall effect in non-collinear antiferromagnetic materials [2-5] and giant anomalous Hall effect in magnetic semimetals [6,7]) continually update our understanding of such a striking but unclear electronic transport phenomenon. Noteworthily, in these materials, the anomalous Hall effect is not simply related to the magnetization that breaks timereversal symmetry; thus, the effect cannot be understood from conventional formation mechanisms. An increasing number of studies have demonstrated that the anomalous Hall effect is intimately connected with the intrinsic Berry-phase effect from spin-orbit couplings. Recent works [1,8] illustrate that anomalous Hall conductivity σ A xy is dominated by σ skew

The discovery of quantum Hall effect in two-dimensional (2D) electronic systems inspired the topological classifications of electronic systems 1,2 . By stacking 2D quantum Hall effects with interlayer coupling much weaker than the Landau level spacing, quasi-2D quantum Hall effects have been experimentally observed 3~7 , due to the similar physical origin of the 2D counterpart. Recently, in a real 3D electronic gas system where the interlayer coupling is much stronger than the Landau level spacing, 3D quantum Hall effect has been observed in ZrTe5 8 . In this Letter, we report the electronic transport features of its sister bulk material, i.e., HfTe5, under external magnetic field. We observe a series of plateaus in Hall resistance ρxy as magnetic field increases until it reaches the quantum limit at 1~2 Tesla. At the plateau regions, the longitudinal resistance ρxx exhibits local

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Recent experiments report a charge density wave (CDW) in the antiferromagnet FeGe, but the nature of the charge ordering and the associated structural distortion remains elusive. We discuss the structural and electronic properties of FeGe. Our proposed ground state phase accurately captures atomic topographies acquired by scanning tunneling microscopy. We show that the 2 × 2 × 1 CDW likely results from the Fermi surface nesting of hexagonal-prism-shaped kagome states. FeGe is found to exhibit distortions in the positions of the Ge atoms instead of the Fe atoms in the kagome layers. Using in-depth first-principles calculations and analytical modeling, we demonstrate that this unconventional distortion is driven by the intertwining of magnetic exchange coupling and CDW interactions in this kagome material. The movement of Ge atoms from their pristine positions also enhances the magnetic moment of the Fe kagome layers. Our study indicates that magnetic kagome lattices provide a material candidate for exploring the effects of strong electronic correlations on the ground state and their implications for transport, magnetic, and optical responses in materials.

We theoretically investigate a folded bilayer graphene structure as an experimentally realizable platform to produce the one-dimensional topological zero-line modes. We demonstrate that the folded bilayer graphene under an external gate potential enables tunable topologically conducting channels to be formed in the folded region, and that a perpendicular magnetic field can be used to enhance the conducting when external impurities are present. We also show experimentally that our proposed folded bilayer graphene structure can be fabricated in a controllable manner. Our proposed system greatly simplifies the technical difficulty in the original proposal by considering a planar bilayer graphene (i.e., precisely manipulating the alignment between vertical and lateral gates on bilayer graphene), laying out a new strategy in designing practical low-power electronics by utilizing the gate induced topological conducting channels.

We explored the possibility of realizing quantum anomalous Hall effect by placing heavy-element atomic layer on top of monolayer CrI3 with a natural cleavage surface and broken time-reversal symmetry. We showed that CrI3/X (X = Bi, Sb, or As) systems can open up a sizable bulk gap to harbour quantum anomalous Hall effect, e.g., CrI3/Bi is a natural magnetic insulator with a bulk gap of 30 meV, which can be further enlarged via strain engineering or adjusting spin orientations. We also found that the ferromagnetic properties (magnetic anisotropic energy and Curie temperature) of pristine CrI3 can be further improved due to the presence of heavy atomic layers, and the spin orientation can be utilized as a useful knob to tune the band structure and Fermi level of CrI3/Bi system. The topological nature, together with the enhanced ferromagnetism, can unlock new potential applications for CrI3-based materials in spintronics and electronics.

Motivated by recent experimental results for zero-line modes (ZLMs) in a bilayer graphene system [Nature Nanotechnol. 11, 1060], we systematically studied the influence of a magnetic field on ZLMs and demonstrated the physical origin of the enhanced robustness by employing nonequilibrium Green's functions and the Landauer-Büttiker formula. We found that a perpendicular magnetic field can separate the wavefunctions of the counter-propagating kink states into opposite directions. Specifically, the separation vanishes at the charge neutrality point. The separation increases as the Fermi level deviates from the charge neutrality point and can reach a magnitude comparable to the wavefunction spread at a moderate field strength. Such spatial separation of oppositely propagating ZLMs effectively suppresses backscattering. Moreover, the presence of a magnetic field enlarges the bulk gap and suppresses the bound states, thereby further reducing the scattering. These mechanisms effectively increase the mean free paths of the ZLMs to approximately 1 µm in the presence of a disorder.