Triple dot system coupled to topological insulators: A numerical renormalization group analysis of the SU(3) attractive Anderson model

Moca, Cătălin Paşcu; Roman, A.; Toderas, M.; Chirla, Razvan

doi:10.1063/1.5017436

AIP Conference Proceedings

2017

DOI: 10.1063/1.5017436

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Triple dot system coupled to topological insulators: A numerical renormalization group analysis of the SU(3) attractive Anderson model

Cătălin Paşcu Moca

A. Roman

M. Toderas

et al.

Abstract: Abstract. We consider the SU(3) attractive Anderson model, which can be realized in a triple-dot system, coupled to external leads that support chiral edge modes, and study its spectral and transport properties using the renormalization group approach. At the symmetric point, where the average occupation is n = 3/2, a resonance develops in the spectral functions, which differs significantly from the regular Kondo effect, and corresponds to trionic processes between states with zero and triple occupation of the… Show more

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Flavor fluctuations in three-level quantum dots: Generic SU(3) Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium

Lindner¹,

Kugler²,

Schoeller³

et al. 2018

Phys. Rev. B

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We study a 3-level quantum dot in the singly occupied cotunneling regime coupled via a generic tunneling matrix to several multi-channel leads in equilibrium or nonequilibrium. Denoting the three possible states of the quantum dot by the quark flavors up (u), down (d) and strange (s), we derive an effective model where also each reservoir has three flavors labelled by u, d and s with an effective density of states polarized w.r.t. an eight-dimensional F -spin corresponding to the eight generators of SU (3). In equilibrium we perform a standard poor man scaling analysis and show that tunneling via virtual intermediate states induces flavor fluctuations on the dot which become SU (3)-symmetric at a characteristic and exponentially small low-energy scale TK . Close to TK the system is described by a single isotropic Kondo coupling J > 0 diverging at TK . Using the numerical renormalization group (NRG) we study in detail the linear conductance and confirm the SU (3)-symmetric Kondo fixed point with universal conductance G = 3 sin 2 (π/3) e 2 h = 2.25 e 2 h for various tunneling setups by tuning the level spacings on the dot. We also identify regions of the level positions where the SU (2)-Kondo fixed point is obtained and find a rather complex dependence of the various Kondo temperatures as function of the gate voltage and the tunneling couplings. In contrast to the equilibrium case, we find in nonequilibrium that the fixed point model is not SU (3)symmetric but characterized by rotated F -spins for each reservoir with total vanishing sum. At large voltage we analyse the F -spin magnetization and the current in golden rule as function of a longitudinal (hz) and perpendicular (h ⊥ ) magnetic field for the isospin and the level spacing ∆ to the strange quark. As a smoking gun to detect the nonequilibrium fixed point we find that the curve of zero F -spin magnetization in (hz, h ⊥ , ∆)-space is a circle when projected onto the (hz, h ⊥ ) plane. We propose that our findings can be generalized to the case of quantum dots with an arbitrary number N of levels.

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Flavor fluctuations in three-level quantum dots: Generic SU(3) Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium

Lindner¹,

Kugler²,

Schoeller³

et al. 2018

Phys. Rev. B

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show abstract

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Triple dot system coupled to topological insulators: A numerical renormalization group analysis of the SU(3) attractive Anderson model

Cited by 1 publication

References 23 publications

Flavor fluctuations in three-level quantum dots: Generic SU(3) Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium

Flavor fluctuations in three-level quantum dots: Generic SU(3) Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium

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