Publications (25)
Measuring the intrinsic charge transfer gap using K-edge X-ray absorption spectroscopy
C. Gougoussis, M. Calandra, A. Seitsonen +3
Pre-edge features in X-ray absorption spectroscopy contain key information about the lowest excited states and thus on the most interesting physical properties of the system. In tr…
Violation of Ioffe-Regel condition but saturation of resistivity of the high Tc cuprates
M. Calandra, O. Gunnarsson
We demonstrate that the resistivity data of a number of high Tc cuprates, in particular La(2-x)SrxCuO4, are consistent with resistivity saturation, although the Ioffe-Regel conditi…
Wannier interpolation of the electron-phonon matrix elements in polar semiconductors: Polar-optical coupling in GaAs
J. Sjakste, N. Vast, M. Calandra +1
We generalize the Wannier interpolation of the electron-phonon matrix elements to the case of polar-optical coupling in polar semiconductors. We verify our methodological developme…
Multiple pre-edge structures in Cu K-edge of high Tc cuprates revealed by high resolution x-ray absorption spectroscopy
C. Gougoussis, J. -P. Rueff, M. Calandra +7
Using high resolution x-ray absorption spectroscopy and state-of-the-art electronic structure calculations we demonstrate that the pre-edge region at the Cu K-edge of high T cu…
Evidence for non-conventional pairing in NaCoOyHO
Jean-Pascal Rueff, M. Calandra, M. D'astuto +10
We report on first investigation of the lattice dynamics in the novel superconducting material NaCoO1.3HO and the non-hydrated parent compound Na$\_{0.7}…
Numerical study of the two dimensional Heisenberg model by Green Function Monte Carlo at fixed number of walkers
M. Calandra, S. Sorella
We describe in detail a simple and efficient Green Function Monte Carlo technique for computing both the ground state energy and the ground state properties by the ``forward walkin…
X-ray Magnetic and Natural Circular Dichroism from first principles: Calculation of K- and L1-edge spectra
N. Bouldi, N. J. Vollmers, C. G. Delpy-Laplanche +8
An efficient first principles approach to calculate X-ray magnetic circular dichroism (XMCD) and X-ray natural circular dichroism (XNCD) is developed and applied in the near edge r…
Electron localization and possible phase separation in the absence of a charge density wave in single-phase 1T-VS
A. Gauzzi, A. Sellam, G. Rousse +12
We report on a systematic study of the structural, magnetic and transport properties of high-purity 1T-VS powder samples prepared under high pressure. The results differ notabl…
On the importance of measuring accurately LDOS maps using scanning tunneling spectroscopy in materials presenting atom-dependent charge order: the case of the correlated Pb/Si(111) single atomic layer
C. Tresca, T. Bilgeri, G. Menard +11
We show how to properly extract the local charge order in two-dimensional materials from scanning tunneling microscopy/spectroscopy (STM/STS) measurements. When the charge order pr…
Pressure-induced order-disorder phase transition in superconducting CaC6
A. Gauzzi, N. Bendiab, M. d'Astuto +9
By means of synchrotron X-ray diffraction, we studied the effect of high pressure, P, up to 13 GPa on the room temperature crystal structure of superconducting CaC6. In this P rang…
Hole-depletion of ladders in SrCuO induced by correlation effects
V. Ilakovac, C. Gougoussis, M. Calandra +7
The hole distribution in SrCuO is studied by low temperature polarization dependent O K Near-Edge X-ray Absorption Fine Structure measurements and state of the…
Dynamical properties of a strongly correlated model for quarter-filled layered organic molecular crystals
J. Merino, A. Greco, R. H. Mckenzie +1
The dynamical properties of an extended Hubbard model, which is relevant to quarter-filled layered organic molecular crystals, are analyzed. We have computed the dynamical charge c…
Charge fluctuations close to phase separation in the two dimensional t-J model
M. Calandra, F. Becca, S. Sorella
We have studied the t-J model using the Green Function Monte Carlo technique. We have obtained accurate energies well converged in the thermodynamic limit, by performing simulation…
Chiral spin texture in the charge-density-wave phase of the correlated metallic Pb/Si(111) monolayer
C. Tresca, C. Brun, T. Bilgeri +10
We investigate the 1/3 monolayer -Pb/Si(111) surface by scanning tunneling spectroscopy (STS) and fully relativistic first-principles calculations. We study both the high-tempe…
Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
P. Giannozzi, S. Baroni, N. Bonini +30
Quantum ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudop…
Advanced capabilities for materials modelling with Quantum ESPRESSO
P. Giannozzi, O. Andreussi, T. Brumme +47
Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the art electronic-structure techniques, based on density-…
Neutron scattering study of the high energy graphitic phonons in superconducting CaC
M. P. M. Dean, A. C. Walters, C. A. Howard +7
We present the results of a neutron scattering study of the high energy phonons in the superconducting graphite intercalation compound CaC. The study was designed to address hi…
Polarized resonant inelastic x-ray scattering as an ultra-fine probe of excited states in La2CuO4
A. Shukla, M. Calandra, M. Taguchi +3
X-ray absorption is the standard method to probe the unoccupied density of states at a given edge. Here we show that polarized Resonant Inelastic X-Ray Scattering in La2CuO4 at the…
K-edge X-ray absorption spectra in transition metal oxides beyond the single particle approximation: shake-up many body effects
M. Calandra, J. P. Rueff, C. Gougoussis +7
The near edge structure (XANES) in K-edge X-ray absorption spectroscopy (XAS) is a widely used tool for studying electronic and local structure in materials. The precise interpreta…
Comparative study of the phonons in non-superconducting BaC6 and superconducting CaC6 using inelastic x-ray scattering
A. C. Walters, C. A. Howard, M. H. Upton +8
The low energy phonons of two different graphite intercalation compounds (GICs) have been measured as a function of temperature using inelastic x-ray scattering (IXS). In the case…
Electronic thermal conductivity at high temperatures: Violation of the Wiedemann-Franz law in narrow band metals
K. Vafayi, M. Calandra, O. Gunnarsson
We study the electronic part of the thermal conductivity kappa of metals. We present two methods for calculating kappa, a quantum Monte-Carlo (QMC) method and a method where the ph…
Saturation of electrical resistivity
O. Gunnarsson, M. Calandra, J. E. Han
Resistivity saturation is observed in many metallic systems with a large resistivity, i.e., when the resistivity has reached a critical value, its further increase with temperature…
Metal-insulator transition and charge ordering in the extended Hubbard model at one-quarter filling
M. Calandra, J. Merino, Ross H. McKenzie
We study with exact diagonalization the zero temperature properties of the quarter-filled extended Hubbard model on a square lattice. We find that increasing the ratio of the inter…
Saturation of electrical resistivity in metals at large temperatures
M. Calandra, O. Gunnarsson
We present a microscopic model for systems showing resistivity saturation. An essentially exact quantum Monte-Carlo calculation demonstrates that the model describes saturation. We…
Electrical resistivity at large temperatures: Saturation and lack thereof
M. Calandra, O. Gunnarsson
Many transition metal compounds show saturation of the resistivity at high temperatures, T, while the alkali-doped fullerenes and the high-Tc cuprates are usually considered to sho…