Conditions for observing emergent SU(4) symmetry in a double quantum dot
| Autor: | Alex C. Hewson, O. J. Curtin, Daniel J. G. Crow, Johannes Bauer, Y. Nishikawa |
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| Přispěvatelé: | Engineering & Physical Science Research Council (EPSRC) |
| Rok vydání: | 2016 |
| Předmět: |
Fluids & Plasmas
FOS: Physical sciences 02 engineering and technology Numerical renormalization group Fixed point 01 natural sciences COQBLIN-SCHRIEFFER MODEL Condensed Matter - Strongly Correlated Electrons Quantum mechanics Mesoscale and Nanoscale Physics (cond-mat.mes-hall) 0103 physical sciences 010306 general physics Anderson impurity model Physics Science & Technology 02 Physical Sciences Strongly Correlated Electrons (cond-mat.str-el) Condensed Matter - Mesoscale and Nanoscale Physics Condensed matter physics Conductance Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 021001 nanoscience & nanotechnology Thermal conduction Physics Condensed Matter Quantum dot Physical Sciences KONDO Sum rule in quantum mechanics Double quantum 03 Chemical Sciences 0210 nano-technology |
| Zdroj: | Physical Review B. 93 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | 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 $n_{\rm tot}=1$ and $n_{\rm tot}=2$ 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 $n_{\rm tot}=1$ universal SU(4) fixed point. 14 pages and 20 figures |
| Databáze: | OpenAIRE |
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