Search results for "electrons"
showing 10 items of 1325 documents
Nonequilibrium Green's function approach to strongly correlated few-electron quantum dots
2009
The effect of electron-electron scattering on the equilibrium properties of few-electron quantum dots is investigated by means of nonequilibrium Green's function theory. The ground and equilibrium states are self-consistently computed from the Matsubara (imaginary time) Green's function for the spatially inhomogeneous quantum dot system whose constituent charge carriers are treated as spin-polarized. To include correlations, the Dyson equation is solved, starting from a Hartree-Fock reference state, within a conserving (second-order) self-energy approximation where direct and exchange contributions to the electron-electron interaction are included on the same footing. We present results for…
Electrical control of 2D magnetism in bilayer CrI3
2018
The challenge of controlling magnetism using electric fields raises fundamental questions and addresses technological needs such as low-dissipation magnetic memory. The recently reported two-dimensional (2D) magnets provide a new system for studying this problem owing to their unique magnetic properties. For instance, bilayer chromium triiodide (CrI3) behaves as a layered antiferromagnet with a magnetic field-driven metamagnetic transition. Here, we demonstrate electrostatic gate control of magnetism in CrI3 bilayers, probed by magneto-optical Kerr effect (MOKE) microscopy. At fixed magnetic fields near the metamagnetic transition, we realize voltage-controlled switching between antiferroma…
Production and Radiochemical Separation of the Auger Electron Emitter140Nd
2000
Among the Auger electron emitters, the radiolanthanide 140Nd has some unique nuclear properties with potential for endoradiotherapeutic applications. In the present study, 140Nd was produced via the 140Ce(3He,3n) nuclear process at the FZ Julich CV28 cyclotron, irradiating CeO2 with 3He particles of 36 MeV primary energy. Yields of about 5 MBq 140Nd per microAh were experimentally obtained. Batch yields of > 100 MBq 140Nd were reached. 140Nd was separated in 75 +/- 5% radiochemical yield using a two-step process, first by extracting the bulk of the target material according to a Ce(IV)/Nd(III) separation, then by final ion exchange purification.
Interface-Assisted Sign Inversion of Magnetoresistance in Spin Valves Based on Novel Lanthanide Quinoline Molecules
2018
Molecules are proposed to be an efficient medium to host spin-polarized carriers, due to their weak spin relaxation mechanisms. While relatively long spin lifetimes are measured in molecular devices, the most promising route toward device functionalization is to use the chemical versatility of molecules to achieve a deterministic control and manipulation of the electron spin. Here, by combining magnetotransport experiments with element-specific X-ray absorption spectroscopy, this study shows the ability of molecules to modify spin-dependent properties at the interface level via metal–molecule hybridization pathways. In particular, it is described how the formation of hybrid states determine…
Slow magnetic fluctuations and superconductivity in fluorine-doped NdFeAsO
2015
Among the widely studied superconducting iron-pnictide compounds belonging to the Ln1111 family (with Ln a lanthanide), a systematic investigation of the crossover region between the superconducting and the antiferromagnetic phase for the Ln = Nd case has been missing. We fill this gap by focusing on the intermediate doping regime of NdFeAsO(1-x)F(x) by means of dc-magnetometry and muon-spin spectroscopy measurements. The long-range order we detect at low fluorine doping is replaced by short-range magnetic interactions at x = 0.08, where also superconductivity appears. In this case, longitudinal-field muon-spin spectroscopy experiments show clear evidence of slow magnetic fluctuations that …
Anomalous Muon Knight Shift Behavior in a Cd Single Crystal
1983
For the positive muon implanted in a metal the precession frequency shift due to hyperfine fields can be measured with high precision. This provides means to obtain information about the local electronic structure of a hydrogen like impurity in any metal in the indefinitely dilute impurity concentration. Ref. 1 gives a summary of the muon Knight shift (KS) investigations in 18 nontransition (simple) metals and some transition metals and discusses the results in the context of the electronic structure of hydrogen in metals.
Length Scale of the Spin Seebeck Effect
2015
We investigate the origin of the spin Seebeck effect in yttrium iron garnet (YIG) samples for film thicknesses from 20 nm to 50 μm at room temperature and 50 K. Our results reveal a characteristic increase of the longitudinal spin Seebeck effect amplitude with the thickness of the insulating ferrimagnetic YIG, which levels off at a critical thickness that increases with decreasing temperature. The observed behavior cannot be explained as an interface effect or by variations of the material parameters. Comparison to numerical simulations of thermal magnonic spin currents yields qualitative agreement for the thickness dependence resulting from the finite magnon propagation length. This allow…
Combined Theoretical and Experimental Study of the Photophysics of Asulam
2013
The photophysics of the neutral molecular form of the herbicide asulam has been described in a joint experimental and theoretical, at the CASPT2 level, study. The unique π → π* aromatic electronic transition (f, ca. 0.5) shows a weak red-shift as the polarity of the solvent is increased, whereas the fluorescence band undergoes larger red-shifts. Solvatochromic data point to higher dipole moment in the excited state than in the ground state (μ(g)μ(e)). The observed increase in pKa in the excited state (pKa* - pKa, ca. 3) is consistent with the results of the Kamlet-Abboud-Taft and Catalán et al. multiparametric approaches. Fluorescence quantum yield varies with the solvent, higher in water (…
Disorder-induced gap in the normal density of states of the organic superconductorκ-(BEDT-TTF)2Cu[N(CN)2]Br
2015
The local density of states (DOS) of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br, measured by scanning tunneling spectroscopy on in situ cleaved surfaces, reveals a logarithmic suppression near the Fermi edge persisting above the critical temperature T(c). The experimentally observed suppression of the DOS is in excellent agreement with a soft Hubbard gap as predicted by the Anderson-Hubbard model for systems with disorder. The electronic disorder also explains the diminished coherence peaks of the quasi-particle DOS below T(c).
Génération et détection d'électrons chauds dans des dispositifs plasmoniques
2021
Hot carrier-based devices are quite promissing for ultrafast photodetection and toset off enhanced physicochemical reactions. Controlling their generation at the nanoscale within plasmonic devices is a key for the future development of hybrid hot carriers technologies. Indeed, Surface PlasmonPolaritons (SPPs) can be exploited to confine light and enhance the number of excited hot carriers. We aim at studying the excitation and dynamics of hot carriers, enhanced by plasmonics, with two different approaches.In a first approach, we aim at controlling the delocalized generation of hot carriers by a propagative SPP. A plasmonic waveguide with a grating coupler is employed. Hot electrons are indi…