New insights into the nanostructure of innovative thin film solar cells gained by positron annihilation spectroscopy

Recent studies showed that positron annihilation methods can provide key insights into the nanostructure and electronic structure of thin film solar cells. In this study, positron annihilation lifetime spectroscopy (PALS) is applied to investigate CdSe quantum dot (QD) light absorbing layers, providing evidence of positron trapping at the...

Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy

Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs), supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our...

Lindhard and RPA susceptibility computations in extended momentum space in electron-doped cuprates

We present an approximation for efficient calculation of the Lindhard susceptibility ?L(q,?) in a periodic system through the use of simple products of real space functions and the fast Fourier transform (FFT). The method is illustrated by providing ?L(q,?) results for the electron doped cuprate Nd2?xCexCuO4 extended over several Brillouin zones...

Bulk Fermi surface and momentum density in heavily doped La2?xSrxCuO4 using high-resolution Compton scattering and positron annihilation spectroscopies

We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La2?xSrxCuO4 by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory ...

Proposal to determine the Fermi-surface topology of a doped iron-based superconductor using bulk-sensitive Fourier-transform Compton scattering

We have carried out first-principles calculations of the Compton scattering spectra to demonstrate that the filling of the hole Fermi surface in LaO1?xFxFeAs produces a distinct signature in the Fourier-transformed Compton spectrum when the momentum transfer vector lies along the [100] direction. We thus show how the critical concentration xc,...

Direct observation of localization of the minority-spin-band electrons in magnetite below the Verwey temperature

Two-dimensional spin-uncompensated momentum density distributions, ?s2D(p)s, were reconstructed in magnetite at 12 and 300 K from several measured directional magnetic Compton profiles. Mechanical detwinning was used to overcome severe twinning in the single-crystal sample below the Verwey transition. The reconstructed ?s2D(p) in the first...

Role of Oxygen Electrons in the Metal-Insulator Transition in the Magnetoresistive Oxide La2-2xSr1+2xMn2O7 Probed by Compton Scattering

We have studied the [100]-[110] anisotropy of the Compton profile in the bilayer manganite. Quantitative agreement is found between theory and experiment with respect to the anisotropy in the two metallic phases (i.e., the low temperature ferromagnetic and the colossal magnetoresistant phase under a magnetic field of 7 T). Robust signatures of...

Electronic coupling of colloidal CdSe nanocrystals monitored by thin-film positron-electron momentum density methods

The effect of temperature controlled annealing on the confined valence electron states in CdSe nanocrystal arrays, deposited as thin films, was studied using two-dimensional angular correlation of annihilation radiation. A reduction in the intensity by ?35% was observed in a feature of the positron annihilation spectrum upon removal of the...

Magnetic momentum density, Fermi surface, and directional magnetic Compton profiles in LaSr2Mn2O7 and La1.2Sr1.8Mn2O7

Temperature-dependent orbital degree of freedom of a bilayer manganite by magnetic compton scattering

Angle-resolved photoemission spectra, electronic structure, and spin-dependent scattering in Ni1-xFex Permalloys

Two-dimensional folding technique for enhancing Fermi surface signatures in the momentum density: Application to Compton scattering data from an Al-3 at. % Li disordered alloy

Reconstructed three-dimensional electron momentum density in lithium: A Compton scattering study

High-resolution Compton scattering study of the electron momentum density in Al

Electronic structure and magnetism of Fe3-xVxX (X=Si, Ga, and Al) alloys by the KKR-CPA method

a-axis-projected electron-positron-momentum density and positron-annihilation spectra in YBa2Cu3O7-x