Quantum phase transitions and the role of impurity-substrate hybridization in Yu-Shiba-Rusinov states

Huang, Huei-Ping; Drost, Robert; Senkpiel, Jacob; Padurariu, Ciprian; Kubala, Björn; Yeyati, A. Levy; Cuevas, Juan Carlos; Ankerhold, Joachim; Kern, Klaus; Ast, Christian R.

doi:10.1038/s42005-020-00469-0

Cited by 38 publications

(40 citation statements)

References 39 publications

(72 reference statements)

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“…In this case, when the energy crosses the Fermi level at the critical coupling J C , a first-order quantum phase transition between the singlet (screened) and the doublet (unscreened) ground state is expected 49 , 51 . Very recently, a similar force-based scenario has been reported in different systems involving magnetic ad-atoms on top of superconductors 15 , including Fe(Te,Se) 30 . As discussed in Supplementary Note 2 , a similar scenario can in principle explain the sub-gap dispersion discovered here.…”

Section: Resultssupporting

confidence: 62%

“…In-gap states have a long history of shining light into the properties of different host materials, and have allowed to bring insight into gap symmetry and structure, symmetry breaking, or the absence of scattering in topological defects, to name a few [15][16][17][18][19][20][21][22][23][24] . Impurity bound states have also been investigated in chains or arrays of magnetic impurities on superconducting surfaces where they can lead to Majorana edge-states [25][26][27][28] .…”

mentioning

confidence: 99%

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Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45

et al. 2021

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By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe0.55Se0.45, a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTe0.55Se0.45, which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.

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Section: Resultssupporting

confidence: 62%

mentioning

confidence: 99%

Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45

et al. 2021

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“…At the critical exchange coupling, the YSR state appears at E F , i.e., ZBP, with equal contributions from electron and hole parts. The QPT was observed for magnetic impurities or molecules [19,43,[45][46][47]. Our scenario qualitatively differs from them since the ZBP in our case is induced by the rotation of the impurity moment.…”

Section: Methodscontrasting

confidence: 48%

Spin-polarized zero-bias peak from a single magnetic impurity at an s-wave superconductor: first-principles study

Park¹,

Nyári²,

Lászlóffy³

et al. 2021

Preprint

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Magnetic impurities at surfaces of superconductors can induce bound states referred to as Yu-Shiba-Rusinov (YSR) states within superconducting gaps. Understanding of YSR states with spinorbit coupling (SOC) plays a pivotal role in studies of Majorana zero modes. Spin polarization of a zero-bias peak (ZBP) is used to determine its topological nature. Here we investigate the YSR states of single magnetic impurities at the surface of Pb using the fully relativistic first-principles simulations including band structure of Pb and five 3d orbitals of the impurity in the superconducting state. We show that for single Fe and Co impurities, strong SOC can induce a ZBP with rotation of the impurity magnetic moment and that the ZBP has large spin polarization in contrast to effective model studies. Conditions for a ZBP from a single magnetic impurity are discussed. Our results are relevant to longer atomic chains considering their canting and noncollinear magnetism.

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“…We find discrete energy levels E n and the shape of electron and hole wave functions , of CdGM vortex bound states (with n the angular momentum number). Magnetic YSR impurities are characterized as usual by the exchange coupling J at the impurity sites 30 . This coupling leads to an effective Hamiltonian in the subspace spanned by the states ψ n −1 , ψ n , ψ n +1 , with solution , .…”

Section: Resultsmentioning

confidence: 99%

Coherent coupling between vortex bound states and magnetic impurities in 2D layered superconductors

et al. 2021

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Bound states in superconductors are expected to exhibit a spatially resolved electron-hole asymmetry which is the hallmark of their quantum nature. This asymmetry manifests as oscillations at the Fermi wavelength, which is usually tiny and thus washed out by thermal broadening or by scattering at defects. Here we demonstrate theoretically and confirm experimentally that, when coupled to magnetic impurities, bound states in a vortex core exhibit an emergent axial electron-hole asymmetry on a much longer scale, set by the coherence length. We study vortices in 2H-NbSe2 and in 2H-NbSe1.8S0.2 with magnetic impurities, characterizing these with detailed Hubbard-corrected density functional calculations. We find that the induced electron-hole imbalance depends on the band character of the superconducting material. Our results show that coupling between quantum bound states in superconductors is remarkably robust and has a strong influence in tunneling measurements.

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Quantum phase transitions and the role of impurity-substrate hybridization in Yu-Shiba-Rusinov states

Cited by 38 publications

References 39 publications

Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45

Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45

Spin-polarized zero-bias peak from a single magnetic impurity at an s-wave superconductor: first-principles study

Coherent coupling between vortex bound states and magnetic impurities in 2D layered superconductors

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