Photoemission spectroscopy

About: Photoemission spectroscopy is a research topic. Over the lifetime, 10821 publications have been published within this topic receiving 250888 citations. The topic is also known as: photoelectron spectroscopy & PES.

Final-state effects in the x-ray photoelectron spectra of cubic sodium-tungsten bronzes

Abstract: Core-electron, valence-, and conduction-band spectra of the cubic sodium-tungsten bronzes ${\mathrm{Na}}_{x}\mathrm{W}{\mathrm{O}}_{3}$ have been obtained by x-ray photoelectron spectroscopy. The samples were vacuum-cleaved single crystals spanning the entire cubic composition range. The band spectra are consistent with the theoretical band structure, and the filling of the conduction band with increasing $x$ is explicitly demonstrated. Sodium and oxygen core-electron spectra have binding energies fixed relative to the bottom of the conduction band and exhibit the plasmon satellites expected on the basis of optical and energy-loss measurements. The unique satellite structure of the tungsten $4f$ electrons is discussed in terms of an excitation of the conduction-band electrons during the photoemission process.

Quantum-spin-Hall insulator with a large gap: single-layer 1T' WSe$_2$

Abstract: Two-dimensional (2D) topological insulators (TIs) are promising platforms for low-dissipation spintronic devices based on the quantum spin Hall (QSH) effect, but experimental realization of such systems with a large band gap suitable for room-temperature applications has proven difficult. Here, we report the successful growth on bilayer graphene of a quasi-freestanding WSe$_2$ single layer with the 1T' structure that does not exist in the bulk form of WSe$_2$. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we observed a gap of 129 meV in the 1T' layer and an in-gap edge state located near the layer boundary. The system's 2D TI characters are confirmed by first-principles calculations. The observed gap diminishes with doping by Rb adsorption, ultimately leading to an insulator-semimetal transition. The discovery of this large-gap 2D TI with a tunable band gap opens up opportunities for developing advanced nanoscale systems and quantum devices.

Characterization of β-SiC surfaces and the Au/SiC interface

Abstract: The chemistry of the β‐SiC surface has been studied with Auger electron spectroscopy (AES) and x‐ray photoemission spectroscopy (XPS). The chemically etched surface was found to be nearly stoichiometric, with only a small amount of adsorbed oxygen, which appears to be localized on the Si states. Ion sputtering caused the surface to become Si rich. Compared to Si, the β‐SiC surface was very resistant to oxidation by air exposure at room temperature and when annealed in O2 at 300 °C. In addition, essentially no reaction occurred between Au and etched β‐SiC even after extensive heat treatment.

Direct determination of mode-projected electron-phonon coupling in the time domain.

Abstract: Ultrafast spectroscopies have become an important tool for elucidating the microscopic description and dynamical properties of quantum materials. In particular, by tracking the dynamics of nonthermal electrons, a material's dominant scattering processes can be revealed. Here, we present a method for extracting the electron-phonon coupling strength in the time domain, using time- and angle-resolved photoemission spectroscopy (TR-ARPES). This method is demonstrated in graphite, where we investigate the dynamics of photoinjected electrons at the [Formula: see text] point, detecting quantized energy-loss processes that correspond to the emission of strongly coupled optical phonons. We show that the observed characteristic time scale for spectral weight transfer mediated by phonon-scattering processes allows for the direct quantitative extraction of electron-phonon matrix elements for specific modes.