Conditions for observing emergent SU(4) symmetry in a double quantum dot

Abstract

We analyze conditions for the observation of a low energy SU(4) fixed point in capacitively coupled quantum dots. One problem, due to dots with different couplings to their baths, has been considered by Tosi, Roura-Bas and Aligia (2015). They showed how symmetry can be effectively restored via the adjustment of individual gates voltages, but they make the assumption of infinite on-dot and inter-dot interaction strengths. A related problem is the difference in the magnitudes between the on-dot and interdot strengths for capacitively coupled quantum dots. Here we examine both factors, based on a two site Anderson model, using the numerical renormalization group to calculate the local spectral densities on the dots and the renormalized parameters that specify the low energy fixed point. Our results support the conclusions of Tosi et al. that low energy SU(4) symmetry can be restored, but asymptotically achieved only if the inter-dot interaction $U_{12}$ is greater than or of the order of the band width of the coupled conduction bath $D$, which might be difficult to achieve experimentally. By comparing the SU(4) Kondo results for a total dot occupation $n_{\mathrm{tot}}=1$ and $n_{\mathrm{tot}}=2$ we conclude that the temperature dependence of the conductance is largely determined by the constraints of the Friedel sum rule rather than the SU(4) symmetry and suggest that an initial increase of the conductance with temperature is a distinguishing characteristic feature of an $n_{\mathrm{tot}}=1$ universal SU(4) fixed point.

arXiv comment14 pages and 20 figures

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• The SU(4) Kondo effect in double quantum dots with ferromagnetic leads
• Majorana mode leaking into a spin-charge entangled double quantum dot
• 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
• Abrupt disappearance and reemergence of the SU(2) and SU(4) Kondo effects due to population inversion
• The $SU(4)-SU(2)$ crossover and spin filter properties of a double quantum dot nanosystem
• Field-Enhanced Kondo Correlations in a Half-Filling Nanotube Dot: Evolution of an SU(N) Fermi-Liquid Fixed Point
• Manipulability of the Kondo effect in a T-shaped triple-quantum-dot structure
• Width of the charge-transfer peak in the SU(N) impurity Anderson model and its relevance to non-equilibrium transport
• 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
• SU(4) Kondo entanglement in double quantum dot devices
• Impact of electron-phonon coupling on electron transport through T-shaped arrangements of quantum dots in the Kondo regime