Abstract Angle-resolved Photoemission Spectroscopy Research Articles

Recent progress in angle-resolved photoemission spectroscopy

Abstract Angle-resolved photoemission spectroscopy (ARPES) is a well-established experimental technique that allows probing of the electronic structure of quantum materials using relatively high-energy photons. ARPES has been extensively used to study important classes of materials such as topological insulators, high-temperature superconductors, two-dimensional materials or interface systems. Although the technique was originally developed over 60 years ago, the last decade has witnessed significant advancements in instrumentation. In this review, we survey recent progress in ARPES, with a focus on developments in novel light sources and electron detection methods, which enable the expansion of ARPES into spin-, time-, or space-resolved domains. Important examples of ARPES results are presented, together with an outlook for the field.

Antinodal kink in the band dispersion of electron-doped cuprate La2\u2212xCexCuO4\xb1\u03b4

Angle-resolved photoemission spectroscopy (ARPES) measurements have established the phenomenon of kink in band dispersion of high-Tc cuprate superconductors. However, systematic studies of the kink in electron-doped cuprates are still lacking experimentally. We performed in situ ARPES measurements on La2−xCexCuO4±δ (LCCO) thin films over a wide electron doping (n) range from 0.05 to 0.23. While the nodal kink is nearly invisible, an antinodal kink around 45 meV, surviving above 200 K, is observed for n ~ 0.05–0.19, whose position is roughly independent of doping. The fact that the antinodal kink observed at high temperatures and in the highly overdoped region favors the phonon mechanism with contributions from the Cu–O bond-stretching mode and the out-of-plane oxygen buckling mode.

Development of an analytical simulation framework for angle-resolved photoemission spectra

Angle-resolved photoemission spectroscopy (ARPES) is probably the most important experimental technique for the investigation of the electronic structure of solids. With respect to the interpretation of measured complex photoemission spectra, extensive theoretical efforts are often involved, as one needs a calculation of the band structure, a mapping of the band structure to the observed complex photoemission spectrum, and the inclusion of many-body effects. Typical methods that include the mentioned necessary steps for the interpretation are usually theoretically costly (such as time-dependent density functional theory). In contrast to purely numerical methods, analytical physical theories grant an easier approach in the implementation and, in general, allow for a more direct insight into the involved physical processes. Here, we show that combining a Keldysh Green's function formulation of the photoelectric current, together with a tight-binding parametrization of band structures, gives a powerful tool set for the simulation of ARPES spectra. Our approach is fast, capable of including many-body effects, and easy to be implemented and, therefore, from the viewpoint of an experimentalist, a valuable tool for the interpretation of photoemission spectra.

More than electrons.

Angle-resolved photoemission spectroscopy of MoS2 doped with Rb atoms unveiled the existence of polarons, whose presence seems to coincide with the onset of superconductivity.

The Effect of Copper on the Electronic Structure and Effective Masses of CuIn5Se8 Single Crystals Revealed by Angle-Resolved Photoemission Spectroscopy

Angle-resolved photoemission spectroscopy (ARPES) has been used to study the electronic structure of InSe and CuIn5Se8 single crystals and determine the general patterns of its transformation after the introduction of copper. The main dispersion curves of valence bands in the studied multicomponent systems and the effective masses of majority carriers in CuIn5Se8 have been obtained. Joint theoretical and experimental research has allowed us to apply ARPES not only to single isolated states, but also to complex crystals with a large number of atoms in the unit cell (and, consequently, a large number of dispersion bands). It has been demonstrated that the neighborhoods of maxima and minima of dispersion curves E(k), which essentially define the set of experimental ARPES spectra, make the dominant contribution to the observed signal intensity.

Method to map one-dimensional electronic wave function by using multiple Brillouin zone angle resolved photoemission

Angle resolved photoemission spectroscopy (ARPES) is a powerful tool to investigate electronic structures of solids and has been widely used in studying various materials. Electronic structure information by ARPES is obtained in the momentum space. However, in the case of one-dimensional systems, we show that real space information can be extracted from ARPES data taken over multiple Brillouin zones (BZs). Intensities in multiple BZs are proportional to the photoemission matrix element which contains information on the coefficient of Bloch wave functions. It is shown that the Bloch wave function coefficients can be indeed extracted from ARPES data, which allows us to construct the real space wave function. As a test, we use ARPES data from proto-typical onedimensional system SrCuO2 and construct the real space wave function.

Relation between the one-particle spectral function and dynamic spin susceptibility of superconductingBi2Sr2CaCu2O8−δ

Angle-resolved photoemission spectroscopy (ARPES) provides a detailed view of the renormalized band structure and, consequently, is a key to the self-energy and the single-particle Green's function. Here, we summarize the ARPES data accumulated over the whole Brillouin zone for the optimally doped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8\ensuremath{-}\ensuremath{\delta}}$ into a parametric model of the Green's function, which we use for calculating the itinerant component of the dynamic spin susceptibility in absolute units with many-body effects taken into account. By comparison with inelastic neutron scattering (INS) data, we show that the itinerant component of the spin response can account for the integral intensity of the experimental INS spectrum. Taking into account the bilayer splitting, we explain the magnetic resonances in the acoustic (odd) and optic (even) INS channels.

Reevaluation of the coupling to a bosonic mode of the charge carriers in(Bi,Pb)2Sr2CaCu2O8+δat the antinodal point

Angle-resolved photoemission spectroscopy (ARPES) is used to study the spectral function of the optimally doped high-T$_c$ superconductor (Bi,Pb)$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ in the vicinity of the antinodal point in the superconducting state. Using a parameterized self-energy function, it was possible to describe both the coherent and the incoherent spectral weight of the bonding and the antibonding band. The renormalization effects can be assigned to a very strong coupling to the magnetic resonance mode and at higher energies to a bandwidth renormalization by a factor of two, probably caused by a coupling to a continuum. The present reevaluation of the ARPES data allows to come to a more reliable determination of the value of the coupling strength of the charge carriers to the mode. The experimental results for the dressing of the charge carriers are compared to theoretical models.

Effects of the doping and the number of planes on the shadow bands of Bi-based cuprates

Angle resolved photoemission spectroscopy (ARPES) has been used to investigate the shadow bands present at the Fermi surface of bismuth based superconductors. Bi2Sr2CaCu2O8+δ (Bi2212) single crystals with different doping levels and Bi2Sr2CuO6+δ (Bi2201) thin films have been studied by means of momentum distribution curves along the Γ Y high symmetry direction in two different Brillouin zones and for an extensive photon energy range. The results show an enhancement of the shadow band intensity in the second Brillouin zone for photon energies around hν = 30 eV. Furthermore, the ratio Shadow Bands/Main Band is shown to be constant as a function of both the doping level and the number of CuO2 planes. An interpretation of this observation on the basis of the current theoretical models will be provided.

Hydrogen adsorption on a HfC(111) surface: angle-resolved photoemission study

Abstract Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the adsorption of hydrogen on a HfC(111) surface. It is found that hydrogen adsorbs dissociatively on the HfC(111) surface forming a (1×1) overlayer at the saturation coverage. A H1s-induced bonding state which is split-off from the substrate valence band is found at 7.2 eV at the Γ point. In addition, another H-induced state is found at just below the Fermi level in off-normal-emission spectra, and the state is ascribed to an extrinsic surface state caused through the H-induced modification of surface electronic states.

Electronic structure of the (1 x 1) oxygen overlayer on TiC(111): Angle-resolved photoemission study.

Angle-resolved photoemission spectroscopy with synchrotron radiation has been used to study the electronic state of oxygen adsorbed on a TiC(111) surface at room temperature. Oxygen is adsorbed dissociatively forming a (1×1) overlayer on the TiC(111) surface at saturation coverage. The band structure of the (1×1)-O overlayer is measured in the two symmetry directions; (Γ M) and (Γ K)of the TiC(111) surface

The low temperature CO/H coadsorption state on NiP{100}: X-ray absorption and photoemission studies

Angle-resolved photoemission and X-ray absorption spectroscopy have been used to re-examine the electronic structure and orientation of the low-temperature CO/H-coadsorption state observed on the N{100} surface. Although the C-O axis remains perpendicular to the surface, the photoemission spectrum is different from that of the pure Ni{100} system, showing some evidence for satellite structure. A comparison is made with CO on Cu{100}, a similar weak chemisorption system.