391 research outputs found
Differential reflection spectroscopy on InAs/GaAs quantum dots
In this report, we present the derivation of the differential reflection
spectrum as has been reported in \emph{Phys. Rev. B} \textbf{72}, 195301
(2005)
Theory of Resonant Inelastic X-ray Scattering by Collective Magnetic Excitations
I present a tractable theory for the Resonant Inelastic X-ray Scattering
(RIXS) spectral function of magnons. The low-energy transition operator is
written as a product of local spin operators times fundamental x-ray absorption
spectra. This leads to simple selection rules for the magnetic cross section.
The scattering cross section linear (quadratic) in spin operators is
proportional to the magnetic circular (linear) dichroic absorption. RIXS is a
novel tool to measure magnetic quasi particles (magnons) and the incoherent
spectral weight, as well as multiple magnons up to very high energy losses, in
small samples, thin films and multilayers, complementary to Neutron scattering
Exploring small energy scales with x-ray absorption and dichroism
Soft x-ray linear and circular dichroism (XLD, XMCD) experiments at the Ce
M edges are being used to determine the energy scales characterizing
the Ce degrees of freedom in the ultrathin ordered surface intermetallic
CeAg/Ag(111). We find that all relevant interactions, i. e. Kondo
scattering, crystal field splitting and magnetic exchange coupling occur on
small scales. Our study demonstrates the usefulness of combining x-ray
absorption experiments probing linear and circular dichroism owing to their
strong sensitivity for anisotropies in both charge distribution and
paramagnetic response, respectively.Comment: 5 pages, 4 figure
Symmetry analysis of magneto-optical effects: The case of x-ray diffraction and x-ray absorption at the transition metal L23 edge
A general symmetry analysis of the optical conductivity or scattering tensor
is used to rewrite the conductivity tensor as a sum of fundamental spectra
multiplied by simple functions depending on the local magnetization direction.
Using this formalism, we present several numerical examples at the transition
metal L23 edge. From these numerical calculations we can conclude that large
deviations from the magneto-optical effects in spherical symmetry are found.
These findings are in particular important for resonant x-ray diffraction
experiments where the polarization dependence and azimuthal dependence of the
scattered Bragg intensity is used to determine the local ordered magnetization
direction
Effective Operator for Transitions in Nonresonant Inelastic X-ray Scattering
Recent experiments by Larson et al. demonstrate the feasibility of measuring
local excitations using nonresonant inelastic X-ray scattering (IXS). We
establish a general framework for the interpretation where the transitions
created in the scattering process are expressed in effective one-particle
operators that follow a simple selection rule. The different operators can be
selectively probed by employing their different dependence on the direction and
magnitude of the transferred momentum. We use the operators to explain the
presence of nodal directions and the nonresonant IXS in specific directions and
planes. We demonstrate how nonresonant IXS can be used to extract valuable
ground state information for orbiton excitations in manganite
- …