181 research outputs found
Kondo Physics and Exact Solvability of Double Dots Systems
We study two double dot systems, one with dots in parallel and one with dots
in series, and argue they admit an exact solution via the Bethe ansatz. In the
case of parallel dots we exploit the exact solution to extract the behavior of
the linear response conductance. The linear response conductance of the
parallel dot system possesses multiple Kondo effects, including a Kondo effect
enhanced by a nonpertubative antiferromagnetic RKKY interaction, has
conductance zeros in the mixed valence regime, and obeys a non-trivial form of
the Friedel sum rule.Comment: 4 pages, 2 figures; v2: published form to appear in August 2007 issue
of Phys. Rev. Let
On Ising Correlation Functions with Boundary Magnetic Field
Exact expressions of the boundary state and the form factors of the Ising
model are used to derive differential equations for the one-point functions of
the energy and magnetization operators of the model in the presence of a
boundary magnetic field. We also obtain explicit formulas for the massless
limit of the one-point and two-point functions of the energy operator.Comment: 19 pages, 5 uu-figures, macros: harvmac.tex and epsf.tex three
references adde
Orbital Dependence of Quasiparticle Lifetimes in Sr2RuO4
Using a phenomenological Hamiltonian, we investigate the quasiparticle
lifetimes and dispersions in the three low energy bands, gamma, beta, and alpha
of Sr2RuO4. Couplings in the Hamiltonian are fixed so as to produce the mass
renormalization as measured in magneto-oscillation experiments. We thus find
reasonable agreement in all bands between our computed lifetimes and those
measured in ARPES experiments by Kidd et al. [1] and Ingle et al. [2]. In
comparing computed to measured quasiparticle dispersions, we however find good
agreement in the alpha-band alone.Comment: 7 pages, 5 figure
Studying the Perturbed Wess-Zumino-Novikov-Witten SU(2)k Theory Using the Truncated Conformal Spectrum Approach
We study the Wess-Zumino-Novikov-Witten (WZNW) theory perturbed by
the trace of the primary field in the adjoint representation, a theory
governing the low-energy behaviour of a class of strongly correlated electronic
systems. While the model is non-integrable, its dynamics can be investigated
using the numerical technique of the truncated conformal spectrum approach
combined with numerical and analytical renormalization groups (TCSA+RG). The
numerical results so obtained provide support for a semiclassical analysis
valid at . Namely, we find that the low energy behavior is sensitive to
the sign of the coupling constant, . Moreover for this
behavior depends on whether is even or odd. With even, we find
definitive evidence that the model at low energies is equivalent to the massive
sigma model. For odd, the numerical evidence is more equivocal, but
we find indications that the low energy effective theory is critical.Comment: 30 pages, 19 eps figures, LaTeX2e file. Version 2: manuscript
accepted for publication; small changes in text and in one of the figure
Interference effects in interacting quantum dots
In this paper we study the interplay between interference effects in quantum
dots (manifested through the appearance of Fano resonances in the conductance),
and interactions taken into account in the self-consistent Hartree-Fock
approximation. In the non-interacting case we find that interference may lead
to the observation of more than one conductance peak per dot level as a
function of an applied gate voltage. This may explain recent experimental
findings, which were thought to be caused by interaction effects. For the
interacting case we find a wide variety of different interesting phenomena.
These include both monotonous and non-monotonous filling of the dot levels as a
function of an applied gate voltage, which may occur continuously or even
discontinuously. In many cases a combination of the different effects can occur
in the same sample. The behavior of the population influences, in turn, the
conductance lineshape, causing broadening and asymmetry of narrow peaks, and
determining whether there will be a zero transmission point. We elucidate the
essential role of the interference between the dot levels in determining these
outcomes. The effects of finite temperatures on the results are also examined.Comment: 11 pages, 9 fugures, REVTeX
Magnetic Response in the Underdoped Cuprates
We examine the dynamical magnetic response of the underdoped cuprates by
employing a phenomenological theory of a doped resonant valence bond state
where the Fermi surface is truncated into four pockets. This theory predicts a
resonant spin response which with increasing energy (0 to 100meV) appears as an
hourglass. The very low energy spin response is found at (pi,pi +- delta) and
(pi +- delta,pi) and is determined by scattering from the pockets' frontside to
the tips of opposite pockets where a van Hove singularity resides. At energies
beyond 100 meV, strong scattering is seen from (pi,0) to (pi,pi). This theory
thus provides a semi-quantitative description of the spin response seen in both
INS and RIXS experiments at all relevant energy scales
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