Stefan Hellmann
(University of Kiel, Germany)
04/04/2011, 16:30
Poster
The combination of time-resolved core-level photoemission spectroscopy using the free-electron laser FLASH and time- and angle-resolved photoemission spectroscopy with a table-top higher-harmonics-generation source opens the way to study the nonequilibrium dynamics of condensed matter systems with full momentum, elemental, chemical, and atomic-site selectivity. We present our experimental...
Hans Christian Schneider
(University of Kaiserslautern)
04/04/2011, 16:30
Poster
We present a theoretical investigation of spin correlations and ordering effects in a one-dimensional Kondo-lattice system, which we study for parameters that are typical of ferromagnetic semiconductors. We set up the general dynamical equations of motion for the spin correlations between itinerant and localized spins including interactions between correlations and densities at the scattering...
Christoph Jung
(Universität Hamburg)
04/04/2011, 16:30
Poster
We present a generalization of the recently developed Superperturbation solver for the Anderson impurity model for the non-equilibrium case. We show that the general dual perturbation theory can be formulated on the Keldysh contour. Starting from a reference Hamiltonian system, in which the time-dependent solution is found by exact diagonalization, we make a dual perturbation expansion in...
Karol Hricovini
(LPMS, Université de Cergy-Pontoise)
04/04/2011, 16:30
Poster
We present dynamics studies by spin-resolved photoemission (S-PES) experiments on magnetite (Fe3O4), a potentially spintronic suitable material. This ferrimagnet with a high Curie temperature has been theoretically predicted to be a half-metallic material with a conductive minority-spin channel and a semiconducting majority-spin channel, resulting in 100 % spin polarisation at the Fermi level...
Takashi Oka
(University of Tokyo)
04/04/2011, 16:30
Poster
We calculate the photo-carrier creation rate in the half-filled Hubbard model in strong AC electric fields. This is done by combining the imaginary time method with the Bethe ansatz wave function, which was developed in ref. [1] in order to study the many-body Schwinger-Landau-Zener mechanism in DC electric fields. The present result is a many-body generalization of the creation rate obtained...
Steven Johnson
(Paul Scherrer Institut)
04/04/2011, 16:30
Poster
We report on an experimental demonstration of the ultrafast switching of magnetic order in a single crystal of CuO. In the experiment, a femtosecond laser pulse initiates a transition from a collinear antiferromagentic structure to a spiral, multiferroic magnetic structure. The first steps occur on time scales ranging from 400 fs to 2 ps, depending on the strength of the excitation. At the...
Armin Kleibert
(Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland)
04/04/2011, 16:30
Poster
We have observed a quadratic x-ray magneto-optical effect in near-normal-incidence reflection at the M edges of iron [1]. The effect appears as the magnetically induced rotation of ~0.1° of the polarization plane of linearly polarized x-ray radiation upon reflection. A comparison of the measured rotation spectrum with results from x-ray magnetic linear dichroism data demonstrates that this is...
Peter Barmettler
(Université de Genève)
04/04/2011, 16:30
Poster
We study the unitary time evolution of antiferromagnetic order in anisotropic Heisenberg chains that are initially prepared in a pure quantum state far from equilibrium. Our analysis indicates that the antiferromagnetic order imprinted in the initial state vanishes exponentially. Depending on the anisotropy parameter, oscillatory or nonoscillatory relaxation dynamics is observed. Furthermore,...
Leonard Müller
(DESY)
04/04/2011, 16:30
Poster
Free-electron laser (FEL) sources based on self-amplified spontaneous emission can provide intense and ultra short femtosecond x-ray pulses from the vacuum ultraviolet to the x-ray range. The unique combination of short pulselength and short wavelength allows to investigate a number of dynamic phenomena on otherwise inaccessible scales.
One of the forefront problems in modern magnetism...
Jure Demsar
(Universität Konstanz, FB Physik, D-78457 Konstanz)
04/04/2011, 16:30
Poster
Numerous femtosecond time-resolved studies of relaxation phenomena in high temperature superconductors have been performed over the last 20 years. Several competing theoretical models have been proposed, yet an overall consensus on the underlying relaxation processes is still lacking, largely due to the fact that also their ground state properties are still under debate. On the other hand, no...
Peter Gaal
(University of Potsdam, Institut for Physics and Astronomy)
04/04/2011, 16:30
Poster
We report on the first time-resolved X-ray diffraction experiment at the EDR beamline at BESSY II performed on epitaxial La0.8Sr0.2MnO3 (LSMO) and SrTiO3 (STO) superlattices grown on single crystal STO substrate.
A Ti:Sapphire laser operating at 208 kHz frequency with 350 fs pulse duration was used as a pump beam. The X-ray pulses from a bending magnet were monochromotized using a single Ge...
Timm Rohwer
(Christian-Albrechts-Universität zu Kiel)
04/04/2011, 16:30
Poster
Angle resolved photoelectron spectroscopy (ARPES) has proved to be a leading technique in identifying static key properties of complex electron systems. In a pump-probe scheme using femtosecond light pulses this application can be extended to monitor ultrafast changes in the electronic valence structure in response to an intense optical excitation, i.e. photo-induced phase-transitions of...
Alexey Melnikov
(Institute of Spectroscopy Russian Academy of Sciences)
04/04/2011, 16:30
Poster
Ultrafast dynamics of laser excited bismuth were studied by means of wavelength-resolved femtosecond pump-probe technique. Several values of excitation wavelengths from 400 to 2300 nm and a probe femtosecond continuum in 400-900 nm range were used. The analysis of decay traces revealed three processes with relaxation time values of 1 ps, 7 ps and ~ 1 ns ascribed to groups of photoexcited...
