arXiv subjects

Bo Tai

Publications and source records attributed to Bo Tai.

5 recordsLinked to original sources

arXiv2026

Anisotropic anomalous Hall effect in distorted kagome GdTi3Bi4

Topological kagome magnets offer a rich landscape for exploring the intricate interplay of quantum interactions among geometry, topology, spin, and correlation. GdTi3Bi4 crystallizes in layered Ti based kagome nets intertwined with zigzag Gd chains along the a axis and orders antiferromagnetically below 15 K. Here, we present the temperature and field dependent electrical transport of GdTi3Bi4 in different directions. The material exhibits anomalous Hall conductivity (AHC) of 410 S cm-1 at 2 K for B parallel c and it is completely absent for B parallel a, despite the similar magnetization observed in both orientations. This behavior is quite contradictory, as anomalous Hall effect (AHE) typically scales with the magnetization. Through first principles calculations, it is demonstrated that in the presence of time reversal symmetry broken by the Gd 4f sublattice and spin orbit coupling, the magnetization direction controls the orbital mixing in the Ti t2g bands, relocating Berry curvature hot spots and producing the observed orientation selective AHC. The results establish GdTi3Bi4 as platform for investigating new avenues of AHE, such as directional AHE, and thus shed new light on the intricate coupling between magnetic and electronic structures, paving the way for exploring novel quantum phenomena.

cond-mat.mtrl-sci↗

arXiv2020

Tunable anomalous Hall transport in bulk and two-dimensional 1$T$-CrTe$_{2}$: A first-principles study

Layered materials with robust magnetic ordering have been attracting significant research interest. In recent experiments, a new layered material 1$T$-CrTe$_{2}$ has been synthesized and exhibits ferromagnetism above the room temperature. Here, based on first-principles calculations, we investigate the electronic, magnetic, and transport properties of 1$T$-CrTe$_{2}$, both in the bulk and in the two-dimensional (2D) limit. We show that 1$T$-CrTe$_{2}$ can be stable in the monolayer form, and has a low exfoliation energy. The monolayer structure is an intrinsic ferromagnetic metal, which maintains a high Curie temperature above the room temperature. Particularly, we reveal interesting features in the anomalous Hall transport. We show that in the ground state, both bulk and monolayer 1$T$-CrTe$_{2}$ possess vanishing anomalous Hall effect, because the magnetization preserves one vertical mirror symmetry. The anomalous Hall conductivity can be made sizable by tuning the magnetization direction or by uniaxial strains that break the mirror symmetry. The room-temperature 2D ferromagnetism and the tunable anomalous Hall effect make the material a promising platform for nanoscale device applications.

cond-mat.mtrl-sci↗

arXiv2020

Two-dimensional CoSe structures: Intrinsic magnetism, strain-tunable anisotropic valleys, magnetic Weyl point, and antiferromagnetic metal state

The interplay between magnetism, band topology, and electronic correlation in low dimensions has been a fascinating subject of research. Here, we propose two-dimensional (2D) material systems which demonstrate such an interesting interplay. Based on first-principles calculations and structural search algorithms, we identify three lowest energy 2D CoSe structures, termed as the $\alpha$-, $\beta$-, and $\gamma$-CoSe. {We show that $\alpha$- and $\beta$-CoSe are two rare examples of 2D antiferromagnetic metals, which are related to their Fermi surfaces nesting features, and meanwhile, $\gamma$-CoSe is a ferromagnetic metal. They possess a range of interesting physical properties, including anisotropic valleys connected by crystalline symmetries, strain-tunable valley polarization, strain-induced metal-semiconductor and/or magnetic phase transitions, as well as topological band features such as the magnetic Weyl point and the magnetic Weyl loop. Remarkably, all the topological features here are robust against spin-orbit coupling.} Some experimental aspects of our predictions have been discussed.

cond-mat.mtrl-sci↗

arXiv2018

Hybrid Structures and Strain-Tunable Electronic Properties of Carbon Nanothreads

The newly synthesized ultrathin carbon nanothreads have drawn great attention from the carbon community. Here, based on first-principles calculations, we investigate the electronic properties of carbon nanothreads under the influence of two important factors: the Stone-Wales (SW) type defect and the lattice strain. The SW defect is intrinsic to the polymer-I structure of the nanothreads and is a building block for the general hybrid structures. We find that the bandgap of the nanothreads can be tuned by the concentration of SW defects in a wide range of $3.92 \sim 4.82$ eV, interpolating between the bandgaps of $sp^{3}$-(3,0) structure and the polymer-I structure. Under strain, the bandgaps of all the structures, including the hybrid ones, show a nonmonotonic variation: the bandgap first increases with strain, then drops at large strain above 10%. The gap size can be effectively tuned by strain in a wide range ($>0.5$ eV). Interestingly, for $sp^{3}$-(3,0) structure, a switch of band ordering occurs under strain at the valence band maximum, and for the polymer-I structure, an indirect-to-direct-bandgap transition occurs at about 8% strain. The result also indicates that the presence of SW defects tends to stabilize the bandgap size against strain. Our findings suggest the great potential of structure- and strain-engineered carbon nanothreads in optoelectronic and photoelectrochemical applications as well as stress sensors.

cond-mat.mtrl-sci↗

arXiv2017

Tunable Half-metallic Magnetism in Atom-thin Holey Two-dimensional C$_2$N Monolayer

Exploring two-dimensional (2D) materials with magnetic ordering is a focus of current research. It remains a challenge to achieve tunable magnetism in a material of one-atom-thickness without introducing extrinsic magnetic atoms or defects. Here, based on first-principles calculations, we propose that tunable ferromagnetism can be realized in the recently synthesized holey 2D C$_2$N ($h$2D-C$_2$N) monolayer via purely electron doping that can be readily achieved by gating. We show that owing to the prominent van Hove singularity in the band structure, the material exhibits ferromagnetism even at a small doping level. Remarkably, over a wide doping range of 4$\times$10$^{13}$/cm$^2$ to 8$\times$10$^{13}$/cm$^2$, the system becomes half-metallic, with carriers fully spin-polarized. The estimated Curie temperature can be up to 320 K. Besides gating, we find that the magnetism can also be effectively tuned by lattice strain. Our result identifies $h$2D-C$_2$N as the first material with single-atom-thickness that can host gate-tunable room-temperature half-metallic magnetism, suggesting it as a promising platform to explore nanoscale magnetism and flexible spintronic devices.

cond-mat.mtrl-sci↗