756 research outputs found
Violation of the Luttinger sum rule within the Hubbard model on a triangular lattice
The frequency-moment expansion method is developed to analyze the validity of
the Luttinger sum rule within the Mott-Hubbard insulator, as represented by the
generalized Hubbard model at half filling and large . For the particular
case of the Hubbard model with nearest-neighbor hopping on a triangular lattice
lacking the particle-hole symmetry results reveal substantial violation of the
sum rule.Comment: 4 pages, 2 figure
Structure and transport in multi-orbital Kondo systems
We consider Kondo impurity systems with multiple local orbitals, such as rare
earth ions in a metallic host or multi--level quantum dots coupled to metallic
leads. It is shown that the multiplet structure of the local orbitals leads to
multiple Kondo peaks above the Fermi energy , and to ``shadow'' peaks
below . We use a slave boson mean field theory, which recovers the strong
coupling Fermi liquid fixed point, to calculate the Kondo peak positions,
widths, and heights analytically at T=0, and NCA calculations to fit the
temperature dependence of high--resolution photoemission spectra of Ce
compounds. In addition, an approximate conductance quantization for transport
through multi--level quantum dots or single--atom transistors in the Kondo
regime due to a generalized Friedel sum rule is demonstrated.Comment: 4 pages, 3 figures. Invited article, 23rd International Conference on
Low Temperature Physics LT23, Hiroshima, Japan 200
The on-shell self-energy of the uniform electron gas in its weak-correlation limit
The ring-diagram partial summation (or RPA) for the ground-state energy of
the uniform electron gas (with the density parameter ) in its
weak-correlation limit is revisited. It is studied, which treatment
of the self-energy is in agreement with the Hugenholtz-van
Hove (Luttinger-Ward) theorem and which is
not. The correlation part of the lhs h as the RPA asymptotics [in atomic units]. The use of renormalized RPA diagrams for the rhs
yields the similar expression with the sum rule
resulting from three sum rules for the components of and . This
includes in the second order of exchange the sum rule [P. Ziesche, Ann. Phys. (Leipzig), 2006].Comment: 19 pages, 10 figure
Bosonization of Fermi liquids
We bosonize a Fermi liquid in any number of dimensions in the limit of long
wavelengths. From the bosons we construct a set of coherent states which are
related with the displacement of the Fermi surface due to particle-hole
excitations. We show that an interacting hamiltonian in terms of the original
fermions is quadratic in the bosons. We obtain a path integral representation
for the generating functional which in real time, in the semiclassical limit,
gives the Landau equation for sound waves and in the imaginary time gives us
the correct form of the specific heat for a Fermi liquid even with the
corrections due to the interactions between the fermions. We also discuss the
similarities between our results and the physics of quantum crystals.Comment: 42 pages, RevteX, preprint UIUC (1993
Evaluation of the optical conductivity tensor in terms of contour integrations
For the case of finite life-time broadening the standard Kubo-formula for the
optical conductivity tensor is rederived in terms of Green's functions by using
contour integrations, whereby finite temperatures are accounted for by using
the Fermi-Dirac distribution function. For zero life-time broadening, the
present formalism is related to expressions well-known in the literature.
Numerical aspects of how to calculate the corresponding contour integrals are
also outlined.Comment: 8 pages, Latex + 2 figure (Encapsulated Postscript
Formation of atom wires on vicinal silicon
The formation of atomic wires via pseudomorphic step-edge decoration on
vicinal silicon surfaces has been analyzed for Ga on the Si(112) surface using
Scanning Tunneling Microscopy and Density Functional Theory calculations. Based
on a chemical potential analysis involving more than thirty candidate
structures and considering various fabrication procedures, it is concluded that
pseudomorphic growth on stepped Si(112), both under equilibrium and
non-equilibrium conditions, must favor formation of Ga zig-zag chains rather
than linear atom chains. The surface is non-metallic and presents quasi-one
dimensional character in the lowest conduction band.Comment: submitte
Damping of zero sound in Luttinger liquids
We calculate the damping gamma_q of collective density oscillations (zero
sound) in a one-dimensional Fermi gas with dimensionless forward scattering
interaction F and quadratic energy dispersion k^2 / 2 m at zero temperature.
For wave-vectors | q| /k_F small compared with F we find to leading order
gamma_q = v_F^{-1} m^{-2} Y (F) | q |^3, where v_F is the Fermi velocity, k_F
is the Fermi wave-vector, and Y (F) is proportional to F^3 for small F. We also
show that zero-sound damping leads to a finite maximum proportional to |k - k_F
|^{-2 + 2 eta} of the charge peak in the single-particle spectral function,
where eta is the anomalous dimension. Our prediction agrees with photoemission
data for the blue bronze K_{0.3}MoO_3.Comment: final version as published; with more technical details; we have
added a discussion of recent work which appeared after our initial cond-mat
posting; 13 pages, 5 figure
Violation of Luttinger's Theorem in the Two-Dimensional t-J Model
We have calculated the high temperature series for the momentum distribution
function n_k of the 2D t-J model to 12th order in inverse temperature. By
extrapolating the series to T=0.2J we searched for a Fermi surface of the 2D
t-J model. We find that three criteria used for estimating the location of a
Fermi surface violate Luttinger's Theorem, implying the 2D t-J model does not
have an adiabatic connection to a non-interacting model.Comment: 4 pages, 5 figures. Version with grayscale figures available upon
reques
A Supersymmetry approach to billiards with randomly distributed scatterers
The density of states for a chaotic billiard with randomly distributed
point-like scatterers is calculated, doubly averaged over the positions of the
impurities and the shape of the billiard. Truncating the billiard Hamiltonian
to a N x N matrix, an explicit analytic expression is obtained for the case of
broken time-reversal symmetry, depending on rank N of the matrix, number L of
scatterers, and strength of the scattering potential. In the strong coupling
limit a discontinuous change is observed in the density of states as soon as L
exceeds N
Two-dimensional array of magnetic particles: The role of an interaction cutoff
Based on theoretical results and simulations, in two-dimensional arrangements
of a dense dipolar particle system, there are two relevant local dipole
arrangements: (1) a ferromagnetic state with dipoles organized in a triangular
lattice, and (2) an anti-ferromagnetic state with dipoles organized in a square
lattice. In order to accelerate simulation algorithms we search for the
possibility of cutting off the interaction potential. Simulations on a dipolar
two-line system lead to the observation that the ferromagnetic state is much
more sensitive to the interaction cutoff than the corresponding
anti-ferromagnetic state. For (measured in particle diameters)
there is no substantial change in the energetical balance of the ferromagnetic
and anti-ferromagnetic state and the ferromagnetic state slightly dominates
over the anti-ferromagnetic state, while the situation is changed rapidly for
lower interaction cutoff values, leading to the disappearance of the
ferromagnetic ground state. We studied the effect of bending ferromagnetic and
anti-ferromagnetic two-line systems and we observed that the cutoff has a major
impact on the energetical balance of the ferromagnetic and anti-ferromagnetic
state for . Based on our results we argue that is a
reasonable choice for dipole-dipole interaction cutoff in two-dimensional
dipolar hard sphere systems, if one is interested in local ordering.Comment: 8 page
- …