Lifetime of quasi-particles in the nearly-free electron metal Sodium

We report a high-resolution angle-resolved photoemission (ARPES) study of the prototypical nearly-free-electron metal sodium. The observed mass enhancement is slightly smaller than that derived in previous studies. The new results on the lifetime broadening increase the demand for theories beyond the random phase approximation. Our results do not support the proposed strong enhancement of the scattering rates of the charge carriers due to a coupling to spin fluctuations. Moreover, a comparison with earlier electron energy-loss data on sodium yields a strong reduction of the mass enhancement of dipolar electron-hole excitations compared to that of monopole hole excitations, measured by ARPES.Comment: 5 pages, 6 figure

Lifetime of quasiparticles in the nearly free electron metal sodium

We report a high resolution angle resolved photoemission ARPES study of the prototypical nearly free electron metal sodium. The observed mass enhancement is slightly smaller than that derived in previous studies. The new results on the lifetime broadening increase the demand for theories beyond the random phase approximation. Our results do not support the proposed strong enhancement of the scattering rates of the charge carriers due to a coupling to spin fluctuations. Moreover, a comparison with earlier electron energy loss data on sodium yields a strong reduction of the mass enhancement of dipolar electron hole excitations compared to that of monopole hole excitations, measured by ARPE

Study of the Formation and Properties of In–CuPcF4_4 Nanocomposite Materials in the Mode of the Millisecond Recording of Photoelectron Spectra

A study of the formation processes and properties of nanocomposite materials consisting of indium nanoparticles in a thin film of the organic semiconductor copper tetrafluorophthalocyanine (CuPcF$_4$) is presented. The results are obtained by the new setup for dynamic photoelectron spectroscopy, which allows the recording of spectra in a millisecond interval using the ARGUS photoelectron spectrometer and synchrotron radiation (PETRA III/DESY, Germany). The evolution of the core level (CL) spectra: C1s, N1s, and In3d$_{5/2}$ recorded directly during the deposition of indium onto the CuPcF$_4$ surface under ultrahigh vacuum conditions is traced. The thickness of the indium coating during deposition increased from 0 to 5 nm. In this range of coatings, more than 150 spectra are recorded for each CL with a recording rate of 0.1 s/spectrum. The following is established: the significant diffusion of indium atoms deep into the organic matrix is observed; in fact, no chemical interaction of indium with carbon atoms is found; indium atoms are located in places close to pyrrole nitrogen of the CuPcF$_4$ molecule. Apparently, during the interaction of In atoms and pyrrole nitrogen atoms, a negative charge is transferred from indium to the CuPcF$_4$ molecule. Thus, data on the fast-flowing processes of the formation of organometallic In–CuPcF$_4$ interfaces are obtained

Study of the formation and properties of In–CuPcF4_4 nanocomposite materials in the mode of the millisecond recording of photoelectron spectra

International audienceA study of the formation processes and properties of nanocomposite materials consisting of indium nanoparticles in a thin film of the organic semiconductor copper tetrafluorophthalocyanine (CuPcF$_4$) is presented. The results are obtained by the new setup for dynamic photoelectron spectroscopy, which allows the recording of spectra in a millisecond interval using the ARGUS photoelectron spectrometer and synchrotron radiation (PETRA III/DESY, Germany). The evolution of the core level (CL) spectra: C1s, N1s, and In3d 5/2 recorded directly during the deposition of indium onto the CuPcF$_4$ surface under ultrahigh vacuum conditions is traced. The thickness of the indium coating during deposition increased from 0 to 5 nm. In this range of coatings, more than 150 spectra are recorded for each CL with a recording rate of 0.1 s/spectrum. The following is established: the significant diffusion of indium atoms deep into the organic matrix is observed; in fact, no chemical interaction of indium with carbon atoms is found; indium atoms are located in places close to pyrrole nitrogen of the CuPcF$_4$ molecule. Apparently, during the interaction of In atoms and pyrrole nitrogen atoms, a negative charge is transferred from indium to the CuPcF$_4$ molecule. Thus, data on the fast-flowing processes of the formation of organometallic In-CuPcF$_4$ interfaces are obtained

Lifetime of quasiparticles in the nearly free electron metal sodium

We report a high-resolution angle-resolved photoemission (ARPES) study of the prototypical nearly free-electron metal sodium. The observed mass enhancement is slightly smaller than that derived in previous studies. The new results on the lifetime broadening increase the demand for theories beyond the random phase approximation. Our results do not support the proposed strong enhancement of the scattering rates of the charge carriers due to a coupling to spin fluctuations. Moreover, a comparison with earlier electron energy-loss data on sodium yields a strong reduction of the mass enhancement of dipolar electron-hole excitations compared to that of monopole hole excitations, measured by ARPES

Noble metal nanoparticles in organic matrix

The purpose of this work is the synthesis and study of the properties of nanocomposite structures created by noble metal (silver) nanoparticles (NP's), an exciting class of materials with unique properties differ from both bulk and atomic behavior, which are self-organize in a thin organic film of copper phthalocyanine (CuPc). The structure and morphology of this material, depending on the amount of deposited silver, was studied in ultrahigh vacuum using transmission electron microscopy (TEM) and photoelectron spectroscopy (PES). Metallic atoms deposited on the surface of an organic substrate diffuse into the substrate, forming NPs with a narrow size distribution, which correlates with the content of the deposited metal. With the help of high-resolution TEM, the distance between the atomic planes of individual silver nanoparticles was determined and the steady gathering of individual nanoparticles into agglomerates and then into nanocrystals with inter-crystallite boundaries was observed. PES revealed a generally weak interaction between silver NPs and the organic matrix. However, a strong band bending in the organic film at small coatings with metal atoms was observed

Nonequilibrium sub–10 nm spin-wave soliton formation in FePt nanoparticles

Magnetic nanoparticles such as FePt in the L10 phase are the bedrock of our current data storage technology. As the grains become smaller to keep up with technological demands, the superparamagnetic limit calls for materials with higher magnetocrystalline anisotropy. This, in turn, reduces the magnetic exchange length to just a few nanometers, enabling magnetic structures to be induced within the nanoparticles. Here, we describe the existence of spin-wave solitons, dynamic localized bound states of spin-wave excitations, in FePt nanoparticles. We show with time-resolved x-ray diffraction and micromagnetic modeling that spin-wave solitons of sub-10 nm sizes form out of the demagnetized state following femtosecond laser excitation. The measured soliton spin precession frequency of 0.1 THz positions this system as a platform to develop novel miniature devices