Transition between SU(4) and SU(2) Kondo effect

L. TOSI, P. ROURA-BAS, A. A. ALIGIA

PHYSICA B - CONDENSED MATTER

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 407 p. 3259 - 3262

0921-4526

Motivated by experiments in nanoscopic systems, we study a generalized Anderson, which consist of two spin degenerate doublets hybridized to a singlet by the promotion of an electron to two conduction bands, as a function of the energy separation d between both doublets. For d=0 or very large, the model is equivalent to a one-level SU(N) Anderson model, with N=4 and 2 respectively. We study the evolution of the spectral density for both doublets (r1(omega) and r2(omega)) and their width in the Kondo limit as d is varied, using the non-crossing approximation (NCA). As d increases, the peak at the Fermi energy in the spectral density (Kondo peak) splits and the density of the doublet of higher energy r2(omega) shifts above the Ferrmi energy. The Kondo temperature TK (determined by the half-width at half maximum of the Kondo peak in density of the doublet of lower energy r1(omega)) decreases dramatically. The variation of TK with d is reproduced by a simple variational calculation.