We have performed electron transport and angle-resolved photo-emission spectroscopy (ARPES) measurements on single crystals of transition metal dipnictide TaAs₂ cleaved along the ( 2 ¯ 01) surface which has the lowest cleavage energy. A Fourier transform of the Shubnikov–de Haas oscillations shows four different peaks whose angular dependence was studied with respect to the angle between magnetic field and the [ 2 ¯ 01] direction. The results indicate elliptical shape of the Fermi surface cross-sections. Additionally, a mobility spectrum analysis was carried out, which also reveals at least four types of carriers contributing to the conductance (two kinds of electrons and two kinds of holes). ARPES spectra were taken on freshly cleaved ( 2 ¯ 01) surface and it was found that bulk states pockets at constant energy surface are elliptical, which confirms the magnetotransport angle dependent studies. First-principles calculations support the interpretation of the experimental results. The theoretical calculations better reproduce the ARPES data if the theoretical Fermi level (FL) is increased, which is due to a small n-doping of the samples. This shifts the FL closer to the Dirac point, allowing investigating the physics of the Dirac and Weyl points, making this compound a platform for the investigation of the Dirac and Weyl points in three-dimensional materials.

${\mathrm{Co}}_{1/3}{\mathrm{NbS}}_2$ is the magnetic intercalate of 2H-${\mathrm{NbS}}_2$ where electronic itinerant and magnetic properties strongly influence each other throughout the phase diagram. Here we report the angle-resolved photoelectron spectroscopy (ARPES) study in ${\mathrm{Co}}_{1/3}{\mathrm{NbS}}_2$. In agreement with previous reports, the observed electronic structure seemingly resembles the one of the parent material 2H-${\mathrm{NbS}}_2$, with the shift in Fermi energy of 0.5 eV accounting for the charge transfer of approximately two electrons from each Co ion into the ${\mathrm{NbS}}_2$ layers. However, in addition, and in contrast to previous reports, we observe significant departures that cannot be explained by the rigid band shift accompanied by minor deformation of bands: First, entirely unrelated to the 2H-${\mathrm{NbS}}_2$ electronic structure, a shallow electronic band is found crossing the Fermi level near the boundary of the first Brillouin zone of ${\mathrm{Co}}_{1/3}{\mathrm{NbS}}_2$. The evolution of the experimental spectra upon varying the incident photon energy suggests the Co origin of this band. Second, the Nb bonding band, found deeply submerged below the Fermi level at the $\mathrm{\Gamma }$ point, indicates that the interlayer hybridization is significantly amplified by intercalation, with Co magnetic ions probably acting as strong covalent bridges between ${\mathrm{NbS}}_2$ layers. The strong hybridization between orbitals that support the itinerant states and the orbitals hosting the local magnetic moments indicates the importance of strong electronic correlations, with the interlayer coupling playing an exquisite role.

LaAgSb${}_2$ is a Dirac semimetal showing charge density wave (CDW) order. Previous angle-resolved photoemission spectroscopy (ARPES) results suggest the existence of the Dirac-cone-like structure in the vicinity of the Fermi level along the $\Gamma$–M direction. This paper is devoted to a complex analysis of the electronic band structure of LaAgSb${}_2$ by means of ARPES and theoretical studies within the ab initio method as well as tight binding model formulation. To investigate the possible surface states, we performed the direct DFT slab calculation and the surface Green function calculation for the (001) surface. The appearance of the surface states, which depends strongly on the surface, points to the conclusion that LaSb termination is realized in the cleaved crystals. Moreover, the surface states predicted by our calculations at the $\Gamma$ and X points are found by ARPES. Nodal lines, which exist along the X–R and M–A paths due to crystal symmetry, are also observed experimentally. The calculations reveal other nodal lines, which originate from the vanishing of spin–orbit splitting and are located at the X–M–A–R plane at the Brillouin zone boundary. In addition, we analyze the band structure along the $\Gamma$–M path to verify whether Dirac surface states can be expected. Their appearance in this region is not confirmed.

The diversity of magnetic orders that appear in layered magnetic materials is of great interest from the fundamental point of view and for applications. In particular, the magnetic sublayers, introduced by intercalation into van der Waals gaps of the host transition-metal dichalcogenide (TMD), are known to produce various magnetic states, with some being tunable by pressure and doping. The magnetic sublayers and their magnetic ordering strongly modify the electronic coupling between layers of the host compound. Understanding the roots of this variability, starting from the underlying electronic structure, is a significant challenge. Here we employ the angle-resolved photoelectron spectroscopy at various photon energies, the ab initio electronic structure calculations, and modeling to address the particular case of Ni-intercalate, ${\mathrm{Ni}}_{1/3}{\mathrm{NbS}}_2$. We find that the bands around the Fermi level bear the signature of a strong yet unusual hybridization between ${\mathrm{NbS}}_2$ conduction band states and the Ni $3d$ orbitals. The hybridization between metallic ${\mathrm{NbS}}_2$ layers is almost entirely suppressed in the central part of the Brillouin zone, including the part of the Fermi surface around the $\mathrm{\Gamma }$ point. Simultaneously, it gets very pronounced towards the zone edges. It is shown that this behavior is the consequence of the rather exceptional, symmetry imposed, spatially strongly varying, zero total hybridization between relevant Ni magnetic orbitals and the neighboring Nb orbitals that constitute the metallic bands. We also report the presence of the so-called $\beta$ feature, discovered only recently in two other magnetic intercalates with very different magnetic orderings. In ${\mathrm{Ni}}_{1/3}{\mathrm{NbS}}_2$, the feature shows only at particular photon energies, indicating its bulk origin. Common to prior observations, it appears as a series of very shallow electron pockets at the Fermi level, positioned along the edge of the Brillouin zone. Unforeseen by ab initio electronic calculations, and its origin still unresolved, the feature appears to be a robust consequence of the intercalation of $2\mathrm{H}\text{−}{\mathrm{NbS}}_2$ with magnetic ions.

We present STM/STS, ARPES and magnetotransport studies of the surface topography and electronic structure of pristine Bi₂Se₃ in comparison to Bi_1.96Mg_0.04Se₃ and Bi_1.98Fe_0.02Se₃. The topography images reveal a large number of complex, triangle-shaped defects at the surface. The local electronic structure of both the defected and non-defected regions is examined by STS. The defect-related states shift together with the Dirac point observed in the undefected area, suggesting that the local electronic structure at the defects is influenced by doping in the same way as the electronic structure of the undefected surface. Additional information about the electronic structure of the samples is provided by ARPES, which reveals the dependence of the bulk and surface electronic bands on doping, including such parameters as the Fermi wave vector. The subtle changes of the surface electronic structure by doping are verified with magneto-transport measurements at low temperatures (200 mK) allowing the detection of Shubnikov-de Haas (SdH) quantum oscillations.

We present study based on ARPES and DFT on the modifications in the electronic structure of MoS₂ resulting from the introduction of sulphur defects by soft annealing and their role in hydrogen adsorption.