156 research outputs found
Boundary TBA Equations for a Non-diagonal Theory
We compute the boundary entropies for the allowed boundary conditions of the
SU(2)-invariant principal chiral model at level k=1. We used the reflection
factors determined in a previous work. As a by-product we obtain some
miscellaneous results such as the ground-state energy for mixed boundary
conditions as well as the degeneracies of the Kondo model in the underscreened
and exactly screened cases. All these computations are in perfect agreement
with known results.Comment: 13 pages, Tex, 2 figures, revised version, added references, to be
published in Nucl. Phys.
Hyperelliptic curves for multi-channel quantum wires and the multi-channel Kondo problem
We study the current in a multi-channel quantum wire and the magnetization in
the multi-channel Kondo problem. We show that at zero temperature they can be
written simply in terms of contour integrals over a (two-dimensional)
hyperelliptic curve. This allows one to easily demonstrate the existence of
weak-coupling to strong-coupling dualities. In the Kondo problem, the curve is
the same for under- and over-screened cases; the only change is in the contour.Comment: 7 pages, 1 figure, revte
Differential equations and duality in massless integrable field theories at zero temperature
Functional relations play a key role in the study of integrable models. We
argue in this paper that for massless field theories at zero temperature, these
relations can in fact be interpreted as monodromy relations. Combined with a
recently discovered duality, this gives a way to bypass the Bethe ansatz, and
compute directly physical quantities as solutions of a linear differential
equation, or as integrals over a hyperelliptic curve. We illustrate these ideas
in details in the case of the theory, and the associated boundary
sine-Gordon model.Comment: 18 pages, harvma
Quantum phase transition in a two-channel-Kondo quantum dot device
We develop a theory of electron transport in a double quantum dot device
recently proposed for the observation of the two-channel Kondo effect. Our
theory provides a strategy for tuning the device to the non-Fermi-liquid fixed
point, which is a quantum critical point in the space of device parameters. We
explore the corresponding quantum phase transition, and make explicit
predictions for behavior of the differential conductance in the vicinity of the
quantum critical point
Exactly Solvable Model of Superconducting Magnetic Alloys
A model describing the Anderson impurity in the Bardeen-Cooper-Schriffer
superconductor is proven to exhibit hidden integrability and is diagonalized
exactly by the Bethe ansatz.Comment: 10 pages, RevTEX, Phys. Lett. A. (in press
On The Multichannel Kondo Model"
A detailed and comprehensive study of the one-impurity multichannel Kondo
model is presented. In the limit of a large number of conduction electron
channels , the low energy fixed point is accessible to a
renormalization group improved perturbative expansion in . This
straightforward approach enables us to examine the scaling, thermodynamics and
dynamical response functions in great detail and make clear the following
features: i) the criticality of the fixed point; ii) the universal non-integer
degeneracy; iii) that the compensating spin cloud has the spatial extent of the
order of one lattice spacing.Comment: 28 pages, REVTEX 2.0. Submitted to J. Phys.: Cond. Mat. Reference
.bbl file is appended at the end. 5 figures in postscript files can be
obtained at [email protected]. The filename is gan.figures.tar.z and
it's compressed. You can uncompress it by using commands: "uncompress
gan.figures.tar.z" and "tar xvf gan.figures.tar". UBC Preprin
Theoretical analysis of the transmission phase shift of a quantum dot in the presence of Kondo correlations
We study the effects of Kondo correlations on the transmission phase shift of
a quantum dot coupled to two leads in comparison with the experimental
determinations made by Aharonov-Bohm (AB) quantum interferometry. We propose
here a theoretical interpretation of these results based on scattering theory
combined with Bethe ansatz calculations. We show that there is a factor of 2
difference between the phase of the S-matrix responsible for the shift in the
AB oscillations, and the one controlling the conductance. Quantitative
agreement is obtained with experimental results for two different values of the
coupling to the leads.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
Kondo effect in two-dimensional disordered electron systems
We investigate the Kondo effect in two-dimensional disordered electron
systems using a finite-temperature quantum Monte Carlo method. Depending on the
position of a magnetic impurity, the local moment is screened or unscreened by
the spin of the conduction electron. On the basis of the results, we show that
the distribution of the Kondo temperature becomes wide and the weight at
becomes large as randomness increases. The average susceptibility shows
a weak power-law or logarithmic divergence at low temperature, indicating a
non-Fermi-liquid behavior.Comment: 2 pages, 2 figures, to be published in supplement of J. Phys. Soc.
Japan, Proceedings of Localisation 2002, (Tokyo, Japan, 2002
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