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

Abstract

Motivated by experiments in nanoscopic systems, we study a generalized Anderson, which consists of two spin degenerate doublets hybridized to a singlet by promotion of an electron to two conduction bands, as a function of the energy separation $\delta$ between both doublets. For $\delta$=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 (${\rho }_{1\sigma }(\omega )$ and ${\rho }_{2\sigma }(\omega )$) and their width in the Kondo limit as $\delta$ is varied, using the non-crossing approximation (NCA). As $\delta$ increases, the peak at the Fermi energy in the spectral density (Kondo peak) splits and the density of the doublet of higher energy ${\rho }_{2\sigma }(\omega )$ 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 ${\rho }_{1\sigma }(\omega )$) decreases dramatically. The variation of $T_K$ with $\delta$ is reproduced by a simple variational calculation.

8 pages, 4 figures. Presented at the conference "Frontiers of Condensed Matter Physics", December 2010

References in corpus (9)

• Orbital Kondo effect in carbon nanotubes
• Evolution of SU(4) Transport Regimes in Carbon Nanotube Quantum Dots
• Kondo Effects in Carbon Nanotubes: From SU(4) to SU(2) symmetry
• Zero-bias conductance in carbon nanotube quantum dots
• Symmetry fingerprints of a benzene single-electron transistor
• Quantum interference in coherent molecular conductance
• Effects of interactions in transport through Aharonov-Bohm-Casher interferometers
• Nonequilibrium dynamics of a singlet-triplet Anderson impurity near the quantum phase transition
• Features of spin-charge separation in the equilibrium conductance through finite rings

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• Enhancing of nonlinear thermoelectric response of a correlated quantum dot in the Kondo regime by asymmetrically coupling to the leads
• Nonequilibrium conductance through a benzene molecule in the Kondo regime
• Restoring the SU(4) Kondo regime in a double quantum dot system
• Relation between width of the zero-bias anomaly and Kondo temperaure in transport measurements through correlated quantum dots: Effect of asymmetric coupling to the leads
• The $SU(4)-SU(2)$ crossover and spin filter properties of a double quantum dot nanosystem
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• Kondo behavior and conductance through $3d$ impurities in gold chains doped with oxygen
• Destructive quantum interference in transport through molecules with electron-electron and electron-vibration interactions
• Thermoelectric properties of a double quantum dot out of equilibrium in Kondo and intermediate valence regimes
• Kondo temperature when the Fermi level is near a step in the conduction density of states
• Role of asymmetry in thermoelectric properties of a double quantum dot out of equilibrium