2,739 research outputs found
Criterion for weak spin-orbit coupling in heavy-fermion superconductivity: A numerical renormalization-group study
A criterion for effective irrelevancy of the spin-orbit coupling in the
heavy-fermion superconductivity is discussed on the basis of the impurity
Anderson model with two sets of Kramers doublets. Using Wilson's numerical
renormalization-group method, we demonstrate a formation of the quasiparticle
as well as the renormalization of the rotational symmetry-breaking interaction
in the lower Kramers doublet (quasispin) space. A comparison with the quasispin
conserving interaction exhibits the effective irrelevancy of the
symmetry-breaking interaction for the splitting of two doublets Delta larger
than the characteristic energy of the local spin fluctuation T_K. The formula
for the ratio of two interactions is also determined.Comment: 4 pages, 4 figures (2 color figures
Novel correlations in two dimensions: Some exact solutions
We construct a new many-body Hamiltonian with two- and three-body
interactions in two space dimensions and obtain its exact many-body ground
state for an arbitrary number of particles. This ground state has a novel
pairwise correlation. A class of exact solutions for the excited states is also
found. These excited states display an energy spectrum similar to the
Calogero-Sutherland model in one dimension. The model reduces to an analog of
the well-known trigonometric Sutherland model when projected on to a circular
ring.Comment: 8 pages, REVTE
Determination of the phase shifts for interacting electrons connected to reservoirs
We describe a formulation to deduce the phase shifts, which determine the
ground-state properties of interacting quantum-dot systems with the inversion
symmetry, from the fixed-point eigenvalues of the numerical renormalization
group (NRG). Our approach does not assume the specific form of the Hamiltonian
nor the electron-hole symmetry, and it is applicable to a wide class of quantum
impurities connected to noninteracting leads. We apply the method to a triple
dot which is described by a three-site Hubbard chain connected to two
noninteracting leads, and calculate the dc conductance away from half-filling.
The conductance shows the typical Kondo plateaus of Unitary limit in some
regions of the gate voltages, at which the total number of electrons N_el in
the three dots is odd, i.e., N_el =1, 3 and 5. In contrast, the conductance
shows a wide minimum in the gate voltages corresponding to even number of
electrons, N_el = 2 and 4.
We also discuss the parallel conductance of the triple dot connected
transversely to four leads, and show that it can be deduced from the two phase
shifts defined in the two-lead case.Comment: 9 pages, 12 figures: Fig. 12 has been added to discuss T_
Kondo effect in Ce(x)La(1-x)Cu(2.05)Si(2) intermetallics
The magnetic susceptibility and susceptibility anisotropy of the quasi-binary
alloy system Ce(x)La(1-x)Cu(2.05)Si(2) have been studied for low concentration
of Ce ions. The single-ion desc ription is found to be valid for x < 0.1. The
experimental results are discussed in terms of t he degenerate
Coqblin-Schrieffer model with a crystalline electric field splitting Delta =
330 K. The properties of the model, obtained by combining the lowest-order
scaling and the pertur bation theory, provide a satisfactory description of the
experimental data down to 30 K. The e xperimental results between 20 K and 2 K
are explained by the exact solution of the Kondo mode l for an effective
doublet.Comment: 11 pages, 13 Postscript figures, 1 tabl
Orientifolds in N=2 Liouville Theory and its Mirror
We consider unoriented strings in the supersymmetric SL(2,R)/U(1) coset,
which describes the two-dimensional Euclidean black hole, and its mirror dual
N=2 Liouville theory. We analyze the orientifolds of these theories from
several complementary points of view: the parity symmetries of the worldsheet
actions, descent from known AdS_3 parities, and the modular bootstrap method
(in some cases we can also check our results against known constraints coming
from the conformal bootstrap method). Our analysis extends previous work on
orientifolds in Liouville theory, the AdS_3 and SU(2) WZW models and minimal
models. Compared to these cases, we find that the orientifolds of the two
dimensional Euclidean black hole exhibit new intriguing features. Our results
are relevant for the study of orientifolds in the neighborhood of NS5-branes
and for the engineering of four-dimensional chiral gauge theories and gauge
theories with SO and Sp gauge groups with suitable configurations of D-branes
and orientifolds. As an illustration, we discuss an example related to a
configuration of D4-branes and O4-planes in the presence of two parallel
fivebranes.Comment: 47 pages, 2 figures; v2 typos fixed, refs added, improved discussion
of Hanany-Witten setup
Oscillations of the magnetic polarization in a Kondo impurity at finite magnetic fields
The electronic properties of a Kondo impurity are investigated in a magnetic
field using linear response theory. The distribution of electrical charge and
magnetic polarization are calculated in real space. The (small) magnetic field
does not change the charge distribution. However, it unmasks the Kondo cloud.
The (equal) weight of the d-electron components with their magnetic moment up
and down is shifted and the compensating s-electron clouds don't cancel any
longer (a requirement for an experimental detection of the Kondo cloud). In
addition to the net magnetic polarization of the conduction electrons an
oscillating magnetic polarization with a period of half the Fermi wave length
is observed. However, this oscillating magnetic polarization does not show the
long range behavior of Rudermann-Kittel-Kasuya-Yosida oscillations because the
oscillations don't extend beyond the Kondo radius. They represent an internal
electronic structure of the Kondo impurity in a magnetic field. PACS: 75.20.Hr,
71.23.An, 71.27.+
Unified approach to photo and electro-production of mesons with arbitrary spins
A new approach to identify the independent amplitudes along with their
partial wave multipole expansions, for photo and electro-production is
suggested,which is generally applicable to mesons with arbitrary spin-parity.
These amplitudes facilitate direct identification of different resonance
contributions.Comment: 11 page
Microscopic Approach to Magnetism and Superconductivity of -Electron Systems with Filled Skutterudite Structure
In order to gain a deep insight into -electron properties of filled
skutterudite compounds from a microscopic viewpoint, we investigate the
multiorbital Anderson model including Coulomb interactions, spin-orbit
coupling, and crystalline electric field effect. For each case of
=113, where is the number of electrons per rare-earth ion, the
model is analyzed by using the numerical renormalization group (NRG) method to
evaluate magnetic susceptibility and entropy of electron. In order to make
further step to construct a simplified model which can be treated even in a
periodic system, we also analyze the Anderson model constructed based on the
- coupling scheme by using the NRG method. Then, we construct an orbital
degenerate Hubbard model based on the - coupling scheme to investigate
the mechanism of superconductivity of filled skutterudites. In the 2-site
model, we carefully evaluate the superconducting pair susceptibility for the
case of =2 and find that the susceptibility for off-site Cooper pair is
clearly enhanced only in a transition region in which the singlet and triplet
ground states are interchanged.Comment: 14 pages, 11 figures, Typeset with jpsj2.cl
Quantum Mechanics and Thermodynamics of Particles with Distance Dependent Statistics
The general notion of distance dependent statistics in anyon-like systems is
discussed. The two-body problem for such statistics is considered, the general
formula for the second virial coefficient is derived and it is shown that in
the limiting cases it reproduces the known results for ideal anyons.Comment: 9 pages, LATEX Kiev Institute for Theoretical Physics preprint
ITP-93-5E, January 199
Heavy Flavour Baryons in Hyper Central Model
Heavy flavor baryons containing single and double charm (beauty) quarks with
light flavor combinations are studied using the hyper central description of
the three-body problem. The confinement potential is assumed as hyper central
coulomb plus power potential with power index . The ground state
masses of the heavy flavor, and baryons are computed
for different power index, starting from 0.5 to 2.0. The predicted
masses are found to attain a saturated value in each case of quark combinations
beyond the power index .Comment: 10 pages, 4 figure
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