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

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• 作者：L. Tosi^a ; P. Roura-Bas^b ; ^{roura@tandar.cnea.gov.ar} ; A.A. Aligia^a
• 关键词：Anderson model ; Spectral density ; Kondo temperature ; Non-crossing approximation
• 刊名：Physica B
• 出版年：2012
• 期刊代码：53_09214526
• 类别：ph
• 出版时间：15 August, 2012
• 卷：407
• 期：16
• 页码：3259-3262
• 文件大小：281 K

摘要

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 between both doublets. For or very large, the model is equivalent to a one-level SU() Anderson model, with and 2 respectively. We study the evolution of the spectral density for both doublets ( and ) and their width in the Kondo limit as is varied, using the non-crossing approximation (NCA). As increases, the peak at the Fermi energy in the spectral density (Kondo peak) splits and the density of the doublet of higher energy shifts above the Ferrmi energy. The Kondo temperature T_K (determined by the half-width at half maximum of the Kondo peak in density of the doublet of lower energy ) decreases dramatically. The variation of T_K with is reproduced by a simple variational calculation.