Phase diagram and excitations of a Shiba molecule

Yao, Norman Y.; Moca, Cătălin Paşcu; Weymann, Ireneusz; Sau, Jay D.; Lukin, Mikhail D.; Demler, Eugene; Zaránd, Gergely

doi:10.1103/physrevb.90.241108

Cited by 49 publications

(44 citation statements)

References 45 publications

(58 reference statements)

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“…The complexity of crystal-field splitting [19,20], vibrational degrees of freedom [21], spinorbit coupling [22][23][24][25], temperature [26], or external magnetic fields [20] have also been included into the theoretical treatments of single impurities. Theoretical models also discussed the coupling of two magnetic impurities long before their experimental observation [27][28][29][30][31][32][33][34]. Finally, the theoretical considerations expanded on the coupling of magnetic impurities into one-dimensional chains and led to the prediction of Majorana bound states for helical [35,36] and ferromagnetic chains [37,38].…”

mentioning

confidence: 99%

Single magnetic adsorbates on s -wave superconductors

Heinrich¹,

Pascual²,

Franke³

2018

Progress in Surface Science

197

156

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In superconductors, magnetic impurities induce a pair-breaking potential for Cooper pairs, which locally affects the Bogoliubov quasiparticles and gives rise to Yu-Shiba-Rusinov (YSR or Shiba, in short) bound states in the density of states (DoS). These states carry information on the magnetic coupling strength of the impurity with the superconductor, which determines the many-body ground state properties of the system. Recently, the interest in Shiba physics was boosted by the prediction of topological superconductivity and Majorana modes in magnetically coupled chains and arrays of Shiba impurities.Here, we review the physical insights obtained by scanning tunneling microscopy into single magnetic adsorbates on the s-wave superconductor lead (Pb). We explore the tunneling processes into Shiba states, show how magnetic anisotropy affects many-body excitations, and determine the crossing of the many-body groundstate through a quantum phase transition. Finally, we discuss the coupling of impurities into dimers and chains and their relation to Majorana physics. CONTENTS

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mentioning

confidence: 99%

Single magnetic adsorbates on s -wave superconductors

Heinrich¹,

Pascual²,

Franke³

2018

Progress in Surface Science

197

156

View full text Add to dashboard Cite

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“…The proximity of SC induces pairing in QDs [41,42] and tends to suppress the Kondo effect if the superconducting energy gap 2∆ becomes larger than the relevant Kondo temperature T K [40,[43][44][45][46][47][48][49]. Moreover, the strength of SC pairing can greatly affect the Kondo physics in the sub-gap transport regime: For QDs attached to SC and normal contacts, it can enhance the Kondo effect [50][51][52], while for DQD-based Cooper pair splitters, it tends to suppress both the SU(2) and SU(4) Kondo effects [53].…”

Section: Nanostructuresmentioning

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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“…Nevertheless, the phase transition does manifest as a visible spectral discontinuity: there is a kink in the energy of the doublet excitation, and the spectral weights have a jump (results not shown). Alternatively, the radio-frequency spectroscopy could be used 34 . The two-impurity Kondo effect quantum phase transition is thus in principle spectroscopically observable, if only a system with sufficiently suppressed particle exchange could be physically realized 73 .…”

Section: Two-impurity Kondo "Criticality"mentioning

confidence: 99%

Numerical subgap spectroscopy of double quantum dots coupled to superconductors

Žitko

2015

Phys. Rev. B

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Double quantum dot nanostructures embedded between two superconducting leads or in a superconducting ring have complex excitation spectra inside the gap which reveal the competition between different many-body phenomena. We study the corresponding two-impurity Anderson model using the non-perturbative numerical renormalization group (NRG) technique and identify the characteristic features in the spectral function in various parameter regimes. At half-filling, the system always has a singlet ground state. For large hybridization, we observe an inversion of excited inter-dot triplet and singlet states due to the level-repulsion between two sub-gap singlet states. The Shiba doublet states split in two cases: a) at non-zero superconducting phase difference and b) away from half-filling. The most complex structure of sub-gap states is found when one or both dots are in the valence fluctuation regime. Doublet splitting can lead to a parity-changing quantum phase transition to a doublet ground state in some circumstances. In such cases, we observe very different spectral weights for the transitions to singlet or triplet excited Shiba states: the triplet state is best visible on the valence-fluctuating dot, while the singlets are more pronounced on the half-filled dot.

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Phase diagram and excitations of a Shiba molecule

Cited by 49 publications

References 45 publications

Single magnetic adsorbates on s -wave superconductors

Single magnetic adsorbates on s -wave superconductors

Nonlocal pairing as a source of spin exchange and Kondo screening

Numerical subgap spectroscopy of double quantum dots coupled to superconductors

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