Quasiparticle scattering interference in superconducting iron pnictides

Zhang, Yanyang; Fang, Chen; Zhou, Xiaoting; Seo, Kangjun; Tsai, Wei-Feng; Bernevig, B. Andrei; Hu, Jiangping

doi:10.1103/physrevb.80.094528

Cited by 58 publications

(59 citation statements)

References 52 publications

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“…Comparing to the selection rules in Table I, we find that the data is most consistent with an s ± scenario with ∆(k) changing sign between the h and e bands; below the superconducting gap h-h scattering intensities are suppressed while e-h scattering intensities are enhanced for non-magnetic impurities 45,47 . Magnetic impurities in the s ± scenario have the opposite effect.…”

Section: Variation Of the Qpi Intensity And S± Pairingsupporting

confidence: 51%

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Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference

et al. 2014

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Quasiparticle interference, (QPI) by means of scanning tunneling microscopy/spectroscopy (STM/STS), angle resolved photoemission spectroscopy (ARPES), and multi-orbital tight binding calculations is used to investigate the band structure and superconducting order parameter of LiFeAs. Using this combination of techniques we identify intra-and interband scattering vectors between the hole (h) and electron (e) bands in the QPI maps. Discrepancies in the band dispersions inferred from previous ARPES and STM/STS are reconciled by recognizing a difference in the kz sensitivity for the two probes. The observation of both h-h and e-h scattering is exploited using phase-sensitive scattering selection rules for Bogoliubov quasiparticles. From this we demonstrate an s± gap structure, where a sign change occurs in the superconducting order parameter between the e and h bands.

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Section: Variation Of the Qpi Intensity And S± Pairingsupporting

confidence: 51%

“…45 The single impurity approach is justified by the dilute concentration of impurities observed in our sample.…”

Section: Theory Of Multiband Quasiparticle Interferencementioning

confidence: 99%

Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference

et al. 2014

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“…In the first one the phase difference between the two gaps is 0, whereas in the second one it is π so that ∆ 1 /∆ 2 = ±|∆ 1 |/|∆ 2 |. ∆ 1(2) is the pair potential in the band 1(2) [58][59][60].…”

Section: Resultsmentioning

confidence: 99%

“…In a simplified scheme, the structure is reduced to two band models, where the symmetry of the pair potential in each band could be different, and experimental evidence has been favorable to the s ++ and s +− symmetries [58][59][60].…”

Section: Multiband Superconductors S ++ and S +− Symmetriesmentioning

confidence: 99%

Noise cross-correlation and Cooper pair splitting efficiency in multi-teminal superconductor junctions

Gil

Herrera

2017

Solid State Communications

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We analyze the non-local shot noise in a multi-terminal junction formed by two Normal metal leads connected to one superconductor. Using the cross Fano factor and the shot noise, we calculate the efficiency of the Cooper pair splitting. The method is applied to d-wave and iron based superconductors. We determine that the contributions to the noise cross-correlation are due to crossed Andreev reflections (CAR), elastic cotunneling, quasiparticles transmission and local Andreev reflections. In the tunneling limit, the CAR contribute positively to the noise cross-correlation whereas the other processes contribute negatively. Depending on the pair potential symmetry, the CAR are the dominant processes, giving as a result a high efficiency for Cooper pair split. We propose the use of the Fano factor to test the efficiency of a Cooper pair splitter device.

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“…The Fourier transform of the differential conductance scans as function of bias voltage give a fingerprint of the Fermi surface in the normal state and in addition of the k-dependence of the gap function in the SC state. It has by now been successfully applied to a variety of cuprate [6][7][8][9][10][11][12], Fe-pnictides [13][14][15][16][17][18][19], and heavy fermion unconventional superconductors [20][21][22]. There are no STM results yet for the hexagonal pnictide SC SrPtAs.…”

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confidence: 99%

Gap function of hexagonal pnictide superconductor SrPtAs from quasiparticle interference spectrum

Akbari

Thalmeier

2014

EPL

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-The pnictide superconductor SrPtAs has a hexagonal layered structure containing inversion symmetry. It is formed by stacking two inequivalent PtAs layers separated by Sr layers. The former have no local (in-plane) inversion symmetry and therefore a (layer-) staggered Rashba spin orbit coupling appears which splits the three Kramers degenerate bands into six quasi-2D bands. The symmetry of the superconducting state of SrPtAs is unknown. Three candidates, spinsinglet A1g and Eg as well as triplet A2u states have been proposed. We predict the quasiparticle interference (QPI) spectrum for these gap functions in t-matrix Born approximation. We show that distinct differences in the pattern of characteristic QPI wave vectors appear. These results may be important to determine the gap symmetry of SrPtAs by STM-QPI method.Transition metal pnictide superconductors (SC) in particular the Fe-based systems are all of the tetragonal (orthorhombic) structure. The layered Pt-pnictide SrPtAs [1] is the first superconductor (T c = 2.4 K) in that class with hexagonal structure composed of honeycomb Pt-As layers spaced by Sr layers. It may be viewed as a MgB 2 type structure with Mg sites ocuppied by Sr and B sites in an ordered fashion such that Pt-As alternate in the 2D honeycomb layers as well along the hexagonal c-axis. The resulting structure has an overall 3D inversion center whereas the individual layers lack 2D inversion symmetry which is not contained in the C 3v layer point group.Because the electronic states at the Fermi level are mostly of Pt(5d) type with strong spin orbit coupling this leads to a peculiar electronic band structure [2]. Firstly the two inequivalent Pt-As layers have only small interlayer hopping which results in a quasi-2D band structure consisting of three hole bands and associated Fermi surface (FS) columns. Secondly an effective 2D Rashba spin orbit coupling term leads to a large splitting of the three bands which depends on k z in such a way that overall 3D inversion symmetry is restored. This has consequences for the possible superconducting pair states. Due to essentially decoupled layers it is reasonable to assume only intra-layer pairing. Then one can expect features as in the non-centrosymmetric superconductors consisting of a mixture of spin-singlet and triplet pairing of the in-plane order parameter due to lack of local 2D inversion symmetry. For the overall 3D superconducting state even or odd parity classification is restored due to the two inequivalent Sr-Pt layers. The momentum dependence of these unconventional pair states was investigated theoretically by Goryo et al [3] and it was found that even A 1g , E g and odd A 2u states are viable candidates. However sofar there is only few experimental evidence to discriminate between them [4].One of the most powerful recent methods to determine the symmetry of the gap function is STM quasiparticle interference (QPI) technique [5]. The Fourier transform of the differential conductance scans as function of bias voltage give a fingerpr...

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Quasiparticle scattering interference in superconducting iron pnictides

Cited by 58 publications

References 52 publications

Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference

Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference

Noise cross-correlation and Cooper pair splitting efficiency in multi-teminal superconductor junctions

Gap function of hexagonal pnictide superconductor SrPtAs from quasiparticle interference spectrum

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