Bound Fermion states on a vortex line in a type II superconductor

Caroli, C.; Gennes, P. G. de; Matricon, Julien

doi:10.1016/0031-9163(64)90375-0

Cited by 1,280 publications

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“…It has been demonstrated that, in cuprate superconductors, the quasi-particle DOS in a vortex core shows a suppression and two low-energy subgap peaks (or kinks) near the Fermi energy 10-14 . These results, distinct from the theoretical predictions for a superconductor with either s-wave [4][5][6][7] or d-wave [15][16][17][18] pairing symmetry, are still not well understood, but suggest that the ground state of the cuprate superconductors may be gapped, manifesting an unconventional feature of the "normal state". Recently, a new family of HTSCs, iron-based superconductors (iron pnictides), was discovered 19 .…”

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confidence: 57%

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Observation of ordered vortices with Andreev bound states in Ba0.6K0.4Fe2As2

Shan¹,

Wang²,

Shen³

et al. 2011

Nature Phys

126

108

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For a type-II superconductor, when the applied magnetic field is higher than the lower critical value H c1 , the magnetic flux will penetrate into the superconductor and form quantized vortices, which usually are arranged in an Abrikosov lattice. For the newly discovered iron pnictide superconductors, previous measurements have shown that, in electron-doped BaFe 2 As 2 , the vortices form a highly disordered structure 1-3 . In addition, the density of states (DOS) within the vortex cores 1 do not exhibit the Andreev bound states in conventional superconductors 4 -8 . In this Letter, we report the observation of a triangular vortex lattice and the Andreev bound states in hole-doped BaFe 2 As 2 by using a low temperature scanning tunneling microscope (STM). Detailed study of the vortex cores reveals that the spectrum of the Andreev bound states inside the vortex core exhibits a distinct spatial evolution: at the center of the vortex core, it appears as a single peak at 0.5 mV below the Fermi-energy; away from the core center, it gradually evolves into two sub-peaks and they eventually fade out. The drastic differences between the vortex cores of the electron-doped and hole-doped counterparts are illusive to the pairing mechanism of the iron pnictide superconductors.Magnetic flux quantization is one of the important quantum phenomena in the mixed

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confidence: 57%

“…The spectra are quite homogeneous within a bright domain or a dark domain, but differences between the spectra from the bright and the dark domains are noticeable. In general, the gap magnitude is a little 4 smaller and the zero-bias conductance (ZBC) is higher in a dark region. These differences can be seen more clearly when temperature is lowered.…”

mentioning

confidence: 99%

Observation of ordered vortices with Andreev bound states in Ba0.6K0.4Fe2As2

Shan¹,

Wang²,

Shen³

et al. 2011

Nature Phys

126

108

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“…It decreases in magnitude with increasing H but the details of its H and T dependences are not theoretically established. The other term, γ v (H)T, is associated with the vortex cores 10 . Its coefficient varies from γ v (0) = 0 to γ v (H c2 ) = γ n , with a variation that is, at least for a single-band superconductor, linear in H. In most samples of superconducting materials there is a "residual" DOS that produces a normal-state-like contribution to C even in zero field.…”

Section: Contributions To the Specific Heat; Approximations In Thmentioning

confidence: 99%

Specific Heat of Ba_0.59K_0.41Fe₂As₂, an Fe-Pnictide Superconductor with T_c = 36.9 K, and a New Method for Identifying the Electron Contribution

et al. 2015

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We report measurements of the specific heat of Ba 0.59 K 0.41 Fe 2 As 2 , an Fe-pnictide superconductor with T c = 36.9 K, for which there are suggestions of an unusual electron pairing mechanism. We use a new method of analysis of the data to derive the parameters characteristic of the electron contribution. It is based on comparisons of α-model expressions for the electron contribution with the total specific heat, which give the electron contribution directly. It obviates the need in the conventional analyses for an independent, necessarily approximate, determination of the lattice contribution, which is subtracted from the total specific heat to obtain the electron contribution. It eliminates the uncertainties and errors in the electron contribution that follow from the approximations in the determination of the lattice contribution. Our values of the parameters characteristic of the electron contribution differ significantly from those obtained in conventional analyses of specific-heat data for five similar holedoped BaFe 2 As 2 superconductors, which also differ significantly among themselves. For Ba 0.59 K 0.41 Fe 2 As 2 the electron density of states is comprised of contributions from two electron bands with superconducting-state energy gaps that differ by a factor 3.8, with 77% coming from the band with the larger gap. The variation of the specific heat with magnetic field is consistent with extended s-wave pairing, one of the theoretical predictions. The relation between the densities of states and the energy gaps in the two bands is not consistent with a theoretical model based on interband interactions alone. Comparison of the normal-state density of states with band-structure calculations shows an extraordinarily large effective mass 2 enhancement, for which there is no precedent in similar materials and no theoretical explanation.

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“…In conventional s-wave superconductors such as NbSe 2 , the observed quasiparticle tunneling spectrum at the vortex core by Hess et al [17] can be explained successfully in terms of the low-lying quasiparticle bound states as shown by Caroli, de Gennes, and Matricon [18]. In copper-oxide cuprates, the condensate has a d-wave…”

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confidence: 89%

Vortex core excitations in superconductors with frustrated antiferromagnetism

Zhu

Balatsky

2006

Physica C: Superconductivity and its Applications

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Motivated by recent discovery of cobalt oxide and organic superconductors, we apply an effective model with strong antiferromagnetic and superconducting pairing interaction to a related lattice structure. It is found that the antiferromagnetism is highly frustrated and a broken-time-reversalsymmetry chiral d + id ′ -wave pairing state prevails. In the mixed state, we have solved the local electronic structure near the vortex core and found no local induction of antiferromagnetism. This result is in striking contrast to the case of copper oxide superconductors. The calculated local density of states indicates the existence of low-lying quasiparticle bound states inside the vortex core, due to a fully gapped chiral pairing state. The prediction can be directly tested by scanning tunneling microscopy.PACS numbers: 74.20.Rp, 74.25.Jb Recently, superconductivity in the oxyhydrate Na 0.35 CoO 2 · 1.3H 2 O below ∼ 5K was discovered by Takata et al.[1] and confirmed immediately by several groups [2,3,4,5]. Interesting features of this material include: (i) It is believed that the superconductivity comes from CoO 2 layers, similar to that in copper-oxide cuprates.(ii) Co 4+ atoms have spin-1 2 but form a triangular lattice, which frustrates the antiferromagnetism (AF) and thus is a promising candidate for the occurrence of spin-liquid phases [6]. There are also organic superconductors like the κ-(BEDT-TTF) 2 X materials which have a lattice structure very similar to the triangular lattice [7,8]. (iii) Theoretically, the analysis based on the resonant valence bond theory in the framework of the t-J model [9,10,11,12] or on the renormalization group theory within the framework of t-U -J model [13] indicates a wide window of broken-time-reversal-symmetry (BTRS) d+id ′ -wave pairing state in the phase diagram. Other theoretical groups [14,15,16] proposed a p x + ip y -wave pairing state mediated by ferromagnetic fluctuations. Since the ferromagnetism is insensitive to the detailed lattice structure, no frustration effect is expected on a triangular lattice. At this stage, we are not at a position to resolve the pairing state issue. Motivated by recent observation of a superconducting phase diagram of Na x CoO 2 · 1.3H 2 O similar to that of the cuprate superconductors [5], we consider in this Letter a spin-singlet pairing and study the nature of low-lying excitations around a vortex in these new superconductors with frustrated antiferromagnetism. The results can be directly tested by further experiments such as scanning tunneling microscopy (STM), which likely will be carried out soon.In conventional s-wave superconductors such as NbSe 2 , the observed quasiparticle tunneling spectrum at the vortex core by Hess et al. [17] can be explained successfully in terms of the low-lying quasiparticle bound states as shown by Caroli, de Gennes, and Matricon [18]. In copper-oxide cuprates, the condensate has a d-wave t',V' FIG. 1: Lattice structure of a superconductor with frustrated antiferromagnetism. It has a nearest-neighbor h...

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Bound Fermion states on a vortex line in a type II superconductor

Cited by 1,280 publications

References 1 publication

Observation of ordered vortices with Andreev bound states in Ba0.6K0.4Fe2As2

Observation of ordered vortices with Andreev bound states in Ba0.6K0.4Fe2As2

Specific Heat of Ba_0.59K_0.41Fe₂As₂, an Fe-Pnictide Superconductor with T_c = 36.9 K, and a New Method for Identifying the Electron Contribution

Vortex core excitations in superconductors with frustrated antiferromagnetism

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Bound Fermion states on a vortex line in a type II superconductor

Cited by 1,280 publications

References 1 publication

Observation of ordered vortices with Andreev bound states in Ba0.6K0.4Fe2As2

Observation of ordered vortices with Andreev bound states in Ba0.6K0.4Fe2As2

Specific Heat of Ba0.59K0.41Fe2As2, an Fe-Pnictide Superconductor with Tc = 36.9 K, and a New Method for Identifying the Electron Contribution

Vortex core excitations in superconductors with frustrated antiferromagnetism

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Specific Heat of Ba_0.59K_0.41Fe₂As₂, an Fe-Pnictide Superconductor with T_c = 36.9 K, and a New Method for Identifying the Electron Contribution