675 research outputs found
Nonequilibrium thermal Casimir-Polder forces
We study the nonequilibrium Casimir-Polder force on an atom prepared in an
incoherent superposition of internal energy-eigenstates, which is placed in a
magnetoelectric environment of nonuniform temperature. After solving the
coupled atom--field dynamics within the framework of macroscopic quantum
electrodynamics, we derive a general expression for the thermal Casimir-Polder
force.Comment: 5 page
Fine structure of "zero-mode" Landau levels in HgTe/HgCdTe quantum wells
HgTe/HgCdTe quantum wells with the inverted band structure have been probed
using far infrared magneto-spectroscopy. Realistic calculations of Landau level
diagrams have been performed to identify the observed transitions.
Investigations have been greatly focused on the magnetic field dependence of
the peculiar pair of "zero-mode" Landau levels which characteristically split
from the upper conduction and bottom valence bands, and merge under the applied
magnetic field. The observed avoided crossing of these levels is tentatively
attributed to the bulk inversion asymmetry of zinc blend compounds.Comment: 5 pages, 4 figure
Casimir-Polder interaction of atoms with magnetodielectric bodies
A general theory of the Casimir-Polder interaction of single atoms with
dispersing and absorbing magnetodielectric bodies is presented, which is based
on QED in linear, causal media. Both ground-state and excited atoms are
considered. Whereas the Casimir-Polder force acting on a ground-state atom can
conveniently be derived from a perturbative calculation of the atom-field
coupling energy, an atom in an excited state is subject to transient force
components that can only be fully understood by a dynamical treatment based on
the body-assisted vacuum Lorentz force. The results show that the
Casimir-Polder force can be influenced by the body-induced broadening and
shifting of atomic transitions - an effect that is not accounted for within
lowest-order perturbation theory. The theory is used to study the
Casimir-Polder force of a ground-state atom placed within a magnetodielectric
multilayer system, with special emphasis on thick and thin plates as well as a
planar cavity consisting of two thick plates. It is shown how the competing
attractive and repulsive force components related to the electric and magnetic
properties of the medium, respectively, can - for sufficiently strong magnetic
properties - lead to the formation of potential walls and wells.Comment: 16 pages, 6 figures, minor additions and correction
Casimir force on amplifying bodies
Based on a unified approach to macroscopic QED that allows for the inclusion
of amplification in a limited space and frequency range, we study the Casimir
force as a Lorentz force on an arbitrary partially amplifying system of
linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate
that the force on a weakly polarisable/magnetisable amplifying object in the
presence of a purely absorbing environment can be expressed as a sum over the
Casimir--Polder forces on the excited atoms inside the body. As an example, the
resonant force between a plate consisting of a dilute gas of excited atoms and
a perfect mirror is calculated
Quantum Correlated Interstitials and the Hall Resistivity of the Magnetically Induced Wigner Crystal
We study a trial wavefunction for an interstitial in a Wigner crystal. We
find that the electron correlations, ignored in a conventional Hartree-Fock
treatment, dramatically lower the interstitial energy, especially at fillings
close to an incompressible liquid state. The correlation between the
interstitial electron and the lattice electrons at is introduced by
constructing a trial wave- function which bears a Jastrow factor of a Laughlin
state at . For fillings close to but just below , we find
that a perfect Wigner crystal becomes unstable against formation of such
interstitials. It is argued that conduction due to correlated interstitials in
the presence of weak disorder leads to the {\it classical} Hall resistivity, as
seen experimentally.Comment: 10 pages, RevTe
Molecular beam epitaxy of high structural quality Bi2Se3 on lattice matched InP(111) substrates
Epitaxial layers of the topological insulator Bi2Se3 have been grown by
molecular beam epitaxy on laterally lattice-matched InP(111)B substrates. High
resolution X-ray diffraction shows a significant improvement of Bi2Se3 crystal
quality compared to layers deposited on other substrates. The measured full
width at half maximum of the rocking curve is Delta omega=13 arcsec, and the
(omega-2theta) scans exhibit clear layer thickness fringes. Atomic force
microscope images show triangular twin domains with sizes increasing with layer
thickness. The structural quality of the domains is confirmed on the
microscopic level by transmission electron microscopy.Comment: 4 pages, 4 figure
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