9 research outputs found
Superconductivity in the Kondo lattice model
We study the Kondo lattice model with additional attractive interaction
between the conduction electrons within the dynamical mean-field theory using
the numerical renormalization group to solve the effective quantum impurity
problem. In addition to normal-state and magnetic phases we also allow for the
occurrence of a superconducting phase. In the normal phase we observe a very
sensitive dependence of the low-energy scale on the conduction-electron
interaction. We discuss the dependence of the superconducting transition on the
interplay between attractive interaction and Kondo exchange.Comment: Submitted to ICM 2009 Conference Proceeding
Low-energy properties of the Kondo lattice model
We study the zero-temperature properties of the Kondo lattice model within
the dynamical mean-field theory. As impurity solver we use the numerical
renormalization group. We present results for the paramagnetic case showing the
anticipated heavy Fermion physics, including direct evidence for the appearance
of a large Fermi surface for antiferromagnetic exchange interaction. Allowing
for the formation of a Neel state, we observe at finite doping an
antiferromagnetic metal below a critical exchange interaction, which shows a
crossover from a local-moment antiferromagnet with a small Fermi surface for
weak exchange coupling to a heavy-fermion antiferromagnet with a large Fermi
surface for increasing exchange. Including lattice degrees of freedom via an
additional Holstein term we observe a significant suppression of the Kondo
effect, leading to strongly reduced lowenergy scale. For too large
electron-phonon coupling we find a complete collaps of the heavy Fermi liquid
and the formation of polarons.Comment: 11 pages, 7 figure
Anderson lattice with explicit Kondo coupling: general features and the field-induced suppression of heavy-fermion state in ferromagnetic phase
We apply the extended (statistically-consistent, SGA) Gutzwiller-type
approach to the periodic Anderson model (PAM) in an applied magnetic field and
in the strong correlation limit. The finite-U corrections are included
systematically by transforming PAM into the form with Kondo-type interaction
and residual hybridization, appearing both at the same time. This effective
Hamiltonian represents the essence of \textit{Anderson-Kondo lattice model}. We
show that in ferromagnetic phases the low-energy single-particle states are
strongly affected by the presence of the applied magnetic field. We also find
that for large values of hybridization strength the system enters the so-called
\textit{locked heavy fermion state}. In this state the chemical potential lies
in the majority-spin hybridization gap and as a consequence, the system
evolution is insensitive to further increase of the applied field. However, for
a sufficiently strong magnetic field, the system transforms from the locked
state to the fully spin-polarized phase. This is accompanied by a metamagnetic
transition, as well as by drastic reduction of the effective mass of
quasiparticles. In particular, we observe a reduction of effective mass
enhancement in the majority-spin subband by as much as 20% in the fully
polarized state. The findings are consistent with experimental results for
CeLaB compounds. The mass enhancement for the spin-minority
electrons may also diminish with the increasing field, unlike for the
quasiparticles states in a single narrow band in the same limit of strong
correlations
An engineered multicomponent bone marrow niche for the recapitulation of hematopoiesis at ectopic transplantation sites
A Framework for Data-Driven Augmented Reality
This paper presents a new framework to support the creation of augmented reality (AR) applications for educational purposes in physics or engineering lab courses. These applications aim to help students to develop a better understanding of the underlying physics of observed phenomena. For each desired experiment, an AR application is automatically generated from an approximate 3D model of the experimental setup and precomputed simulation data. The applications allow for a visual augmentation of the experiment, where the involved physical quantities like vector fields, particle beams or density fields can be visually overlaid on the real-world setup. Additionally, a parameter feedback module can be used to update the visualization of the physical quantities according to actual experimental parameters in real-time. The proposed framework was evaluated on three different experiments: a Teltron tube with Helmholtz coils, an electron-beam-deflection tube and a parallel plate capacitor
Photoluminescence of carbon nanodots:Dipole emission centers and electron-phonon coupling
Photoluminescence of Carbon Nanodots: Dipole Emission Centers and Electron–Phonon Coupling
Inorganic
carbon nanomaterials, also called carbon nanodots, exhibit
a strong photoluminescence with unusual properties and, thus, have
been the focus of intense research. Nonetheless, the origin of their
photoluminescence is still unclear and the subject of scientific debates.
Here, we present a single particle comprehensive study of carbon nanodot
photoluminescence, which combines emission and lifetime spectroscopy,
defocused emission dipole imaging, azimuthally polarized excitation
dipole scanning, nanocavity-based quantum yield measurements, high
resolution transmission electron microscopy, and atomic force microscopy.
We find that photoluminescent carbon nanodots behave as electric dipoles,
both in absorption and emission, and that their emission originates
from the recombination of photogenerated charges on defect centers
involving a strong coupling between the electronic transition and
collective vibrations of the lattice structure