3,749 research outputs found
Femtosecond study of the interplay between excitons, trions, and carriers in (Cd,Mn)Te quantum wells
We present an absorption study of the neutral and positively charged exciton
(trion) under the influence of a femtosecond, circularly polarized, resonant
pump pulse. Three populations are involved: free holes, excitons, and trions,
all exhibiting transient spin polarization. In particular, a polarization of
the hole gas is created by the formation of trions. The evolution of these
populations is studied, including the spin flip and trion formation processes.
The contributions of several mechanisms to intensity changes are evaluated,
including phase space filling and spin-dependent screening. We propose a new
explanation of the oscillator strength stealing phenomena observed in p-doped
quantum wells, based on the screening of neutral excitons by charge carriers.
We have also found that binding heavy holes into charged excitons excludes them
from the interaction with the rest of the system, so that oscillator strength
stealing is partially blockedComment: 4 pages, 4 figure
An exact solution of the metric-affine gauge theory with dilation, shear, and spin charges
The spacetime of the metric-affine gauge theory of gravity (MAG) encompasses
{\it nonmetricity} and {\it torsion} as post-Riemannian structures. The sources
of MAG are the conserved currents of energy-momentum and dilation, shear and
spin. We present an exact static spherically symmetric vacuum solution of the
theory describing the exterior of a lump of matter carrying mass and dilation,
shear and spin charges.Comment: 13 pages, RevTe
PP-waves with torsion and metric-affine gravity
A classical pp-wave is a 4-dimensional Lorentzian spacetime which admits a
nonvanishing parallel spinor field; here the connection is assumed to be
Levi-Civita. We generalise this definition to metric compatible spacetimes with
torsion and describe basic properties of such spacetimes. We use our
generalised pp-waves for constructing new explicit vacuum solutions of
quadratic metric-affine gravity.Comment: 17 pages, LaTeX2
The anomalous Hall effect in non-collinear antiferromagnetic MnNiN thin films
We have studied the anomalous Hall effect (AHE) in strained thin films of the
frustrated antiferromagnet MnNiN. The AHE does not follow the
conventional relationships with magnetization or longitudinal conductivity and
is enhanced relative to that expected from the magnetization in the
antiferromagnetic state below \,K. This enhancement is
consistent with origins from the non-collinear antiferromagnetic structure, as
the latter is closely related to that found in MnIr and MnPt where
a large AHE is induced by the Berry curvature. As the Berry phase induced AHE
should scale with spin-orbit coupling, yet larger AHE may be found in other
members of the chemically flexible MnN structure
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