Enhanced conductance through side-coupled double quantum dots

Žitko, Rok; Bonča, J.

doi:10.1103/physrevb.73.035332

Cited by 71 publications

(26 citation statements)

References 31 publications

(44 reference statements)

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“…Already the extension to two or three orbital systems has lead to the discovery of striking phenomena such as the ferromagnetic Kondo effect313233 corresponding to a sign change of the exchange coupling, and multistage3536 or frustrated3738394041424344 screening.…”

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confidence: 99%

Kondo blockade due to quantum interference in single-molecule junctions

et al. 2017

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Molecular electronics offers unique scientific and technological possibilities, resulting from both the nanometre scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule junctions: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Here we unify these phenomena, showing that transport through a spin-degenerate molecule can be either enhanced or blocked by Kondo correlations, depending on molecular structure, contacting geometry and applied gate voltages. An exact framework is developed, in terms of which the quantum interference properties of interacting molecular junctions can be systematically studied and understood. We prove that an exact Kondo-mediated conductance node results from destructive interference in exchange-cotunneling. Nonstandard temperature dependences and gate-tunable conductance peaks/nodes are demonstrated for prototypical molecular junctions, illustrating the intricate interplay of quantum effects beyond the single-orbital paradigm.

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confidence: 99%

Kondo blockade due to quantum interference in single-molecule junctions

et al. 2017

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“…2(b). The temperature at which the second stage of screening takes place can be theoretically estimated from [27,28]…”

Section: Relevant Energy Scalesmentioning

confidence: 99%

“…5, the dependence of S S on ε 1 for large p is quite sharp. This is related to Fano-like interference, which occurs between transport paths through a weakly coupled molecular state of DQD that is a resonant one and another, strongly coupled state serving as the background [28,29,31,32]. To shed more light on this behavior, in Fig.…”

Section: Dependence On the Position Of Qd1 Energy Levelmentioning

confidence: 99%

Strong spin Seebeck effect in Kondo T-shaped double quantum dots

Wójcik¹,

Weymann²

2016

J. Phys.: Condens. Matter

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We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads' spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.

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“…Local exchange between the spin of a quantum dot (QD) and the spin of conduction band electrons gives rise to the Kondo effect [2,5]. Direct exchange arriving with an additional side-coupled QD may destroy it or lead to the two-stage Kondo screening [4,[6][7][8][9][10]. In a geometry where the two QDs contact the same lead, conduction band electrons mediate the RKKY exchange [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Nonlocal pairing as a source of spin exchange and Kondo screening

Wójcik¹,

Weymann²

2019

Phys. Rev. B

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We show that the Kondo screening in a correlated double quantum dot structure may be caused solely by the proximity of a superconductor, which induces nonlocal pairing by Andreev reflection processes. This leads to an effective exchange interaction, which we estimate perturbatively and corroborate the analytical predictions by the numerical renormalization group calculations, using an effective model for the superconductor-proximized nanostructure. We determine the dependence of the relevant Kondo temperature on the coupling to superconductor and predict a characteristic modification of conventional low-temperature transport behavior, which can be used to experimentally distinguish this phenomenon from other Kondo effects. The occurrence of nonlocal pairing exchange does not depend on details of the proposed setup, therefore it can be also of relevance for the bulk materials, such as heavy-fermion compounds. arXiv:1809.06415v2 [cond-mat.str-el]

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Enhanced conductance through side-coupled double quantum dots

Cited by 71 publications

References 31 publications

Kondo blockade due to quantum interference in single-molecule junctions

Kondo blockade due to quantum interference in single-molecule junctions

Strong spin Seebeck effect in Kondo T-shaped double quantum dots

Nonlocal pairing as a source of spin exchange and Kondo screening

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