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We study Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ multi-band superconductor with $T_c=14$K by polarization-resolved Raman spectroscopy. Deep in the superconducting state, we detect pair-breaking excitation at 45cm$^{-1}$ ($2\Delta=5.6$meV) in the…

Superconductivity · Physics 2020-04-01 S. -F. Wu , A. Almoalem , I. Feldman , A. Lee , A. Kanigel , G. Blumberg

We consider plane junctions with graphene electrodes, which are formed by a single-level system ("molecule") placed between the edges of two single-layer graphene half planes. We calculate the edge Green functions of the electrodes and the…

Mesoscale and Nanoscale Physics · Physics 2015-06-05 Dmitry A. Ryndyk , Jan Bundesmann , Ming-Hao Liu , Klaus Richter

In the quest for dynamic multimodal probing of a material's structure and functionality, it is critical to be able to quantify the chemical state on the atomic and nanoscale using element specific electronic and structurally sensitive tools…

Iron selenide (FeSe) is an iron-based superconductor which shows unique properties, including strongly anisotropic superconducting gap, paramagnetism in undoped compound and extremely small Fermi pocket size. In this work, we demonstrate…

Superconductivity · Physics 2021-03-17 Wantong Huang , Haicheng Lin , Cheng Zheng , Yuguo Yin , Xi Chen , Shuai-Hua Ji

Two-dimensional electronic spectra (2DES) provide unique ways to track the energy transfer dynamics in light-harvesting complexes. The interpretation of the peaks and structures found in experimentally recorded 2DES is often not…

Biological Physics · Physics 2020-01-07 Tobias Kramer , Mirta Rodríguez

Van der Waals (vdW) materials exhibit intriguing structural, electronic and photonic properties. Electron Energy Loss Spectroscopy (EELS) within Scanning Transmission Electron Microscope (STEM) allows for nanoscale mapping of such…

We study the photoabsorption cross section and Fermi-edge singularities (FES) in graphene. For fillings below one half, we find, besides the expected FES in form of a peaked edge at the threshold (Fermi) energy, a second singularity to…

Mesoscale and Nanoscale Physics · Physics 2011-06-07 Georg Roeder , Grigory Tkachov , Martina Hentschel

In this work we perform electron energy-loss spectroscopy (EELS) of freestanding graphene with high energy and momentum resolution to disentangle the quasielastic scattering from the excitation gap of Dirac electrons close to the optical…

Interpretation of x-ray absorption near-edge structure (XANES) experiments is often done via analyzing the role of particular atoms in the formation of specific peaks in the calculated spectrum. Typically, this is achieved by calculating…

Condensed Matter · Physics 2009-11-07 Ondrej Sipr

The real and imaginary parts of the complex refractive index of SixNyHz have been calculated using density functional perturbation theory. Optical spectra for reflectivity, adsorption coefficient, energy-loss function (ELF), and refractive…

The electronic excitation spectra of undoped, and potassium as well as calcium doped phenantrene-type hydrocarbons have been investigated using electron energy-loss spectroscopy (EELS) in transmission. In the undoped materials, the lowest…

Materials Science · Physics 2015-02-26 Friedrich Roth , Martin Knupfer

We present a computational scheme for extracting the energy level alignment of a metal/molecule interface, based on constrained density functional theory and local exchange and correlation functionals. The method, applied here to benzene on…

Materials Science · Physics 2015-06-17 A. M. Souza , I. Rungger , C. D. Pemmaraju , U. Schwingenschloegl , S. Sanvito

We present an ab initio study of neutral core and valence electronic excitations in {\alpha}-Al2O3 by solving the Bethe-Salpeter equation (BSE) of many-body perturbation theory within an all-electron framework. Calculated spectra at the Al…

Materials Science · Physics 2024-01-26 M. Laura Urquiza , Matteo Gatti , Francesco Sottile

Photonic modes in dielectric nanostructures, e.g., wide gap semiconductor like CeO2 (ceria), has potential for various applications such as light harvesting and information transmission. To fully understand the properties of such phenomenon…

Optics · Physics 2024-08-06 Yifan Wang , Shize Yang , Peter A. Crozier

We study the origin of the structure in the spin-polarized electron energy loss spectroscopy (SPEELS) spectra of ferromagnetic crystals. Our study is based on a 3d tight-binding Fe model, with constant onsite Coulomb repulsion U between…

Materials Science · Physics 2009-10-31 R. Saniz , S. P. Apell

This paper presents the X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopic (XPS) studies of Nd doped phosphate glasses before and after gamma irradiation. The intensity and location of LIII edge white line…

Materials Science · Physics 2015-01-16 V. N. Rai , Parasmani Rajput , S. N. Jha , D. Bhattacharya , B. N. Raja Shekhar

We study the role of the superconducting proximity effect on the electron-phonon energy exchange in diffusive normal metals (N) attached to superconductors (S). The proximity effect modifies the spectral response of the normal metal, in…

Mesoscale and Nanoscale Physics · Physics 2009-03-16 T. T. Heikkila , F. Giazotto

We consider the spin-exchange (SE) cross section in electron scattering from $^3$He\,{\scriptsize II}, which drives the hyperfine-changing \hbox{3.46 cm} (8.665 GHz) line transition. Both the analytical quantum defect method --- applicable…

Atomic Physics · Physics 2015-06-19 Klaus Bartschat , H. R. Sadeghpour

The iron-based superconductors that contain FeAs layers as the fundamental building block in the crystal structures have been rationalized in the past using ideas based on the Fermi Surface nesting of hole and electron pockets when in the…

Superconductivity · Physics 2015-06-11 Elbio Dagotto

Partial substitution of Fe by Ta in the hole-doped La0.5Sr0.5FeO3 decreases the electric conductivity by up to three orders of magnitude. This decrease is in immediate correlation with a decrease of the electron hole concentration and a…