%0 Journal Article
%J PHYSICAL REVIEW B
%D 2003
%T Strong-coupling fixed point instability in a single-channel SU(N) Kondo model
%A Jerez, A
%A Lavagna, M
%A Bensimon, David
%C ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
%I AMERICAN PHYSICAL SOC
%K CONFORMAL-FIELD-THEORY
%K FERMI-LIQUID BEHAVIOR
%K HEAVY FERMIONS
%K IMPURITIES
%K MAGNETIC INSTABILITY
%K METALS
%K OPERATORS
%K PHASE-TRANSITIONS
%K QUANTUM CRITICAL PHENOMENA
%K SYSTEMS
%R 10.1103/PhysRevB.68.094410
%V 68
%X We study a generalized SU(N) single-impurity Kondo model in which the impurity spin is described by a combination of q Abrikosov fermions and (2S-1) Schwinger bosons. Our aim is to describe both the quasiparticlelike excitations and the locally critical modes observed in various physical situations, including non-Fermi-liquid behavior in heavy-fermion systems in the vicinity of a quantum critical point. We carry out an analysis of the strong-coupling fixed point, from which an effective Hamiltonian is derived containing both a charge interaction and a spin coupling between n(d) nearest-neighbor electrons and the screened impurity. The effective charge interaction is already present in the case of a purely fermionic impurity and it changes from repulsive to attractive at q=N/2, due to the q–>N-q symmetry. The sign of the effective spin coupling determines the stability of the strong-coupling fixed point. Already in the single-channel case and in contrast with either the pure bosonic or the pure fermionic case, the strong-coupling fixed point is unstable against the conduction electron kinetic term in the large-N limit as soon as q>N/2. The origin of this change of regime is directly related to the sign of the effective charge interaction.
%8 SEP 1
%9 Article