Coqblin-Schrieffer impurity in a singular metal

Abstract

A Coqblin-Schrieffer impurity of spin $S$ coupled to the boundary of an open SU(N)-invariant $t-J$ chain with $N=2S+2$ is studied. The model is integrable as a function of one coupling parameter $v$ for arbitrary spin and band filling. The system is coupled to a reservoir of electrons and as a function of the chemical potential the host chain has a critical point corresponding to the van Hove singularity of the empty band of charges. In the neighborhood of this critical point we study the low temperature properties of the impurity as a function of $v$. For constant chemical potential we obtain two critical coupling values $v_1=-1/2$ and $v_2=0$ separating phases in which the impurity spin is completely compensated (Kondo effect), partially screened (undercompensated impurity) or decoupled from the chain (free spin). The partial compensation occurs as a consequence of a thermally {\it activated Kondo effect} in the region $v_1<v<v_2$. The possible realization of such a {\it finite temperature Kondo effect} in narrow-gap semiconductors is discussed.

Rextex 5 pages, no figure

References in corpus (4)

• Exact Results for a Kondo Problem in One Dimensional t-J Model
• Overscreening of magnetic impurities in $d_{x^2-y^2}$ wave superconductors
• Hidden Kondo Effect in a Correlated Electron Chain
• Ghost spins and novel quantum critical behavior in a spin chain with local bond-deformation

Cited by in corpus (1)

• On quantum group symmetry and Bethe ansatz for the asymmetric twin spin chain with integrable boundary