Ab initio study of the topological itinerant transport properties observed between excited edge states in a 2D compound with the Mn15B16Ni composition.

We theoretically demonstrate how the competition between band inversion and spin-orbit coupling (SOC) results in the nontrivial topology of band evolution, using two-dimensional (2D) Mn16B16 as a matrix. This study utilizes the ab initio method with the generalized gradient approximation (GGA+U scheme) and Wannier functions to investigate the topological and transport properties of the Ni-doped structure. The Ni atom induces dynamical antilocalization, which appears due to the phase accumulation between time-reversed fermion loops. A key observation is that when band inversion dominates over SOC, "twin" Weyl cones appear in the band structure, in which the Weyl cones caused by the large Berry curvature coupling with the net magnetization lead to the significantly enhanced anomalous Hall conductivity (AHC). Interestingly, the nested small polaron and energy band inversion coexist with SOC. An analysis of the projected energy band shows that the doped Ni atom induces a strong spin wave for both spin up and spin down.

Evolution of local edge state braiding and spin topological transport characterization of Te-doped monolayer 1T'-MoS2.

We conducted first-principles calculations to investigate the dynamic braiding of local edge states and the spin topological transport mechanism in a strong topological MoS1.75Te0.25 matrix. The presence of type-II Van Hove singularity in the middle of the X-S path indicates a strong cohesive interaction and a paring condensation mechanism within the matrix. The surface state data of MoS1.75Te0.25 clearly demonstrate the characteristic features of strong regular loop braiding in spin transport. The spin Hall conductivity of the matrix was determined from the anisotropic characteristics of the spin Berry curvature. The phase transition of the spin Hall conductivity was evidenced by the positive sign of local spin polarization strength, primarily contributed by the dz2 orbital of Mo atoms, and the negative sign of spin polarization strength, mainly contributed by the p-px orbitals of S atoms. Moreover, the inclusion of Te selectively tuned the spin transport efficiency of the dz2 and px orbitals. Comprehensive braiding and readout of edge states can be achieved using an artificially designed MoS1.75Te0.25 spintronic device. This 2D fractional braiding holds significant potential for applications in topological quantum computation.