14 research outputs found
Kondo Effect of a Magnetic Ion Vibrating in a Harmonic Potential
To discuss Kondo effects of a magnetic ion vibrating in the sea of conduction
electrons, a generalized Anderson model is derived. The model includes a new
channel of hybridization associated with phonon emission or absorption. In the
simplest case of the localized electron orbital with the s-wave symmetry,
hybridization with p-waves becomes possible. Interesting interplay among the
conventional s-wave Kondo effect and the p-wave one and the Yu-Anderson type
Kondo effect is found and the ground state phase diagram is determined by using
the numerical renormalization group method. Two different types of stable fixed
points are identified and the two-channel Kondo fixed points are generically
realized on the boundary.Comment: 15 pages, 17 figures, J. Phys. Soc. Jpn. 80 (2011) No.6 to be
publishe
Orbital Kondo behavior from dynamical structural defects
The interaction between an atom moving in a model double-well potential and
the conduction electrons is treated using renormalization group methods in
next-to-leading logarithmic order. A large number of excited states is taken
into account and the Kondo temperature is computed as a function of
barrier parameters. We find that for special parameters can be close to
and it can be of the same order of magnitude as the renormalized
splitting . However, in the perturbative regime we always find that
T_K \alt \Delta with a T_K \alt 1 {\rm K} [Aleiner {\em et al.}, Phys.
Rev. Lett. {\bf 86}, 2629 (2001)]. We also find that remains
unrenormalized at energies above the Debye frequency, .Comment: 9 pages, 9 figures, RevTe
Heavy-Electron Formation and Bipolaronic Transition in the Anharmonic Holstein Model
The emergence of the bipolaronic phase and the formation of the
heavy-electron state in the anharmonic Holstein model are investigated using
the dynamical mean-field theory in combination with the exact diagonalization
method. For a weak anharmonicity, it is confirmed that the first-order
polaron-bipolaron transition occurs from the observation of a discontinuity in
the behavior of several physical quantities. When the anharmonicity is
gradually increased, the polaron-bipolaron transition temperature is reduced as
well as the critical values of the electron-phonon coupling constant for
polaron-bipolaron transition. For a strong anharmonicity, the polaron-bipolaron
transition eventually changes to a crossover behavior. The effect of
anharmonicity on the formation of the heavy-electron state near the
polaron-bipolaron transition and the crossover region is discussed in detail.Comment: 11 pages, 13 figure
First experience with regeneration of moulding mixture based on water-glass
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