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Spin- and angle-resolved photoemission spectroscopy ("spin-ARPES") is a powerful technique for probing the spin degree-of-freedom in materials with nontrivial topology, magnetism, and strong correlations. Spin-ARPES faces severe experimental challenges compared to conventional ARPES attributed to the dramatically lower efficiency of its detection mechanism, making it crucial for instrumentation developments that improve the overall performance of the technique. In this paper, we demonstrate the functionality of our spin-ARPES setup based on time-of-flight spectroscopy and introduce our recent development of an electrostatic deflector mode to map out spin-resolved band structures without sample rotation. We demonstrate the functionality by presenting the spin-resolved spectra of the topological insulator Bi2Te3 and describe in detail the spectrum calibrations based on numerical simulations. By implementing the deflector mode, we minimize the need for sample rotation during measurements, hence improving the overall efficiency of experiments on small or inhomogeneous samples. [ABSTRACT FROM AUTHOR]

The field of two-dimensional (2D) ferromagnetism has been proliferating over the past few years, with ongoing interests in basic science and potential applications in spintronic technology. However, a high-resolution spectroscopic study of the 2D ferromagnet is still lacking due to the small size and air sensitivity of the exfoliated nanoflakes. Here, we report a thickness-dependent ferromagnetism in epitaxially grown Cr2Te3 thin films and investigate the evolution of the underlying electronic structure by synergistic angle-resolved photoemission spectroscopy, scanning tunneling microscopy, x-ray absorption spectroscopy, and first-principle calculations. A conspicuous ferromagnetic transition from Stoner to Heisenberg-type is directly observed in the atomically thin limit, indicating that dimensionality is a powerful tuning knob to manipulate the novel properties of 2D magnetism. Monolayer Cr2Te3 retains robust ferromagnetism, but with a suppressed Curie temperature, due to the drastic drop in the density of states near the Fermi level. Our results establish atomically thin Cr2Te3 as an excellent platform to explore the dual nature of localized and itinerant ferromagnetism in 2D magnets. Over the last few years, several van der Waals materials have been found that retain magnetic ordering down to monolayer thickness. These materials provide a simple platform for studying the magnetism in reduced dimensions. Here, Zhong et al study the thickness dependence of magnetic ordering in Cr2Te3, and find a crossover from Stoner to Heisenberg-type magnetism as thicknesses are reduced. [ABSTRACT FROM AUTHOR]

The low-energy electronic structure of a ferromagnetic insulator Cr 2 Ge 2 Te 6 was studied by angle-resolved photoemission spectroscopy (ARPES). A broadening of the ARPES spectra, which we ascribe to a splitting of the valence band, has been observed at low temperature. Through temperature dependent measurements, we found that the band splitting presented a transition at ∼ 60 –70 K, which is consistent with the ferromagnetic transition temperature of Cr 2 Ge 2 Te 6. Therefore, we suggested that the splitting of the valence band is due to the spin polarization effect of Te 5p states by Cr 3d states, which is compatible with the superexchange coupling through Cr-Te-Cr to form long-range ferromagnetic order in Cr 2 Ge 2 Te 6. [ABSTRACT FROM AUTHOR]

The electronic structure of single-crystalline Ba(Zn0.875Mn0.125)2As2, the parent compound of the recently found high-temperature ferromagnetic semiconductor-(Ba,K)(Zn,Mn)2As2, was studied by high-resolution angle-resolved photoemission spectroscopy. A flat band related to the 3d states of the doped Mn atoms was observed at the binding energy of ~ -1.6 eV besides the previously reported feature at about -3.3 eV. The spectral weight of this feature is much stronger than that obtained from density functional theory calculations. We proposed that the large spectral weight could originate from the hybridization between Mn and As orbitals. The overall band dispersions agree well with the first-principles calculations of undoped BaZn2As2 except that the total bandwidth of the valence band is larger than that calculated. The increased bandwidth after Mn doping is compatible with the proposed theoretical model. [ABSTRACT FROM AUTHOR]

The electronic structure of Sb( 110) is studied by angle-resolved photoemission spectroscopy and first-principles calculations, revealing several electronic surface states in the projected bulk band gaps around the Fermi energy. The dispersion of the states can be interpreted in terms of a strong spin-orbit splitting. The bulk band structure of Sb has the characteristics of a strong topological insulator with a ℤ2 invariant 𝑣0 = 1. This puts constraints on the existence of metallic surface states and the expected topology of the surface Fermi contour. However, bulk Sb is a semimetal, not an insulator, and these constraints are therefore partly relaxed. This relation of bulk topology and expected surface-state dispersion for semimetals is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The growth of tetracene on SiO2/Si(111) substrate has been studied by ultraviolet photoemission spectroscopy measurements. Seven emission features of the organic material are located at 2.26, 3.56, 4.77, 5.88, 6.98, 8.18 and 9.90eV, respectively, below the Fermi level. The changes in binding energy and work function during the deposition of tetracene molecules on SiO2 substrate indicate an interaction between tetracene molecule and substrate. The interaction between tetracene molecule and substrate is weaker than that between the organic and silicon substrate. The reduction in work function is due to the formation of interface dipole. Based on the density functional theory (DFT) calculation, tetracene molecules are arranged in an upright standing manner with the optimal growth of a small cluster consisting four molecules. [Copyright &y& Elsevier]

The electronic structure of single-crystalline Ba(Zn0.875Mn0.125)2As2, the parent compound of the recently found high-temperature ferromagnetic semiconductor-(Ba,K)(Zn,Mn)2As2, was studied by high-resolution angle-resolved photoemission spectroscopy. A flat band related to the 3d states of the doped Mn atoms was observed at the binding energy of ~ -1.6 eV besides the previously reported feature at about -3.3 eV. The spectral weight of this feature is much stronger than that obtained from density functional theory calculations. We proposed that the large spectral weight could originate from the hybridization between Mn and As orbitals. The overall band dispersions agree well with the first-principles calculations of undoped BaZn2As2 except that the total bandwidth of the valence band is larger than that calculated. The increased bandwidth after Mn doping is compatible with the proposed theoretical model. [ABSTRACT FROM AUTHOR]