Competing superconducting and magnetic order parameters and field-induced magnetism in electron-doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Ba</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Co</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:ms

Larsen, Jacob; Uranga, B. Mencia; Stieber, G.; Holm, S. L.; Bernhard, C.; Wolf, Th.; Lefmann, Kim; Andersen, Brian M.; Niedermayer, Ch.

doi:10.1103/physrevb.91.024504

Cited by 10 publications

(11 citation statements)

References 71 publications

(195 reference statements)

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“…. Recent experimental studies have found evidence for the presence of magnetic fluctuations along with superconductivity below T c [51,52]. Studies in FeSe samples have shown evidence for BCS-BEC crossover in a Fermi system with strong spin imbalance, where the presence of preformed pairs in the crossover regime [33] was reported, namely, the possibility of superconducting fluctuations present above T c .…”

Section: Discussionmentioning

confidence: 99%

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe_2−xCo_xAs₂single crystals

et al. 2016

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Increasing doping concentration (x) in pnictide superconductors leads to a loss of long range magnetic order and the emergence of superconductivity. In these doped compounds the role of magnetic fluctuations and their effect on superconductivity is not well understood. Below T c , in optimally doped BaFe 2−x Co x As 2 single crystals at low applied magnetic fields (H), we observe a coexistence of regions with both positive and negative (diamagnetic) magnetization response. With increasing H the positive magnetization response weakens and the diamagnetic signal associated with superconductivity enhances. Above T c , resistivity and magnetization measurements in the normal state of the material reveals the presence of a weak diamagnetic response admixed with the magnetic response of a magnetized state. Magneto-optical imaging studies in the optimally doped sample shows a spatially inhomogeneous local magnetic response in the normal state with local regions having diamagnetic like response existing alongside magnetized regions with short range magnetic order. Above T c , the estimated volume fraction with diamagnetic fluctuations is found to be maximum in the optimally doped sample. We present a doping dependent H-T diagram identifying different fluctuation regimes. We propose our results suggest the admixture of magnetic and superconducting fractions in BaFe 2−x Co x As 2 and a close correlation between them.

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Section: Discussionmentioning

confidence: 99%

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe_2−xCo_xAs₂single crystals

et al. 2016

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“…High resolution synchrotron x-ray data were collected at beamline 11BM-B of the Advanced Photon Source (APS) at Argonne National Laboratory (ANL) with λ = 0.414Å. Detailed structural analyses were performed using the Rietveld method as implemented in the FullProf, GSAS and EXPGUI software suites [21][22][23] . Inelastic neutron scattering (INS) experiments were carried out on HFIR's triple-axis spectrometer HB-3.…”

mentioning

confidence: 99%

“…The 233 family orders in non-centrosymmetric hexagonal P 6m2 space group symmetry with a structural motif of double-walled sub-nano tubes (DWS) coaxial to the caxis and of [(Cr 3 As 3 ) −2 ] ∞ stoichiometry (see Fig. 1(d)) while the A-site ion acting as a spacer/charge reservoir 'layer' 2,4,5 . DFT calculations predict a Fermi surface built of complex mixtures of the Cr 3d shells with strong Q1D character 3,6,7 .…”

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confidence: 99%

Coupling of structure to magnetic and superconducting orders in quasi-one-dimensional K2Cr3As3

et al. 2017

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Quasi-one-dimensional A2Cr3As3 (with A = K, Cs, Rb) is an intriguing new family of superconductors which exhibit many similar features to the cuprate and iron-based unconventional superconductor families. Yet in contrast to these systems, no charge or magnetic ordering has been observed which could provide the electronic correlations presumed necessary for an unconventional superconducting pairing mechanism -an absence which defies predictions of first principles models. We report the results of neutron scattering experiments on polycrystalline K2Cr3As3 (Tc ∼ 7K) which probed the low temperature dynamics near Tc. Neutron diffraction data evidence a strong response of the nuclear lattice to the onset of superconductivity while inelastic scattering reveals a highly dispersive column of intensity at the commensurate wavevector q = (00 1 2 ) which loses intensity beneath Tc -indicative of short-range magnetic fluctuations. Using linear spin-wave theory we model the observed scattering and suggest a possible structure to the short-range magnetic order. These observations suggest that K2Cr3As3 is in close proximity to a magnetic instability and that the incipient magnetic order both couples strongly to the lattice and competes with superconductivity -in direct analogy with the iron-based superconductors.PACS numbers: 74.25. Dw, 74.62.Dh, 74.70.Xa, 61.05.fm Understanding how superconductivity arises from myriad competing ground states and exotic phenomena such as quantum criticality has been an overarching theme in the study of unconventional superconductors (UNSC) -particularly in the well-studied quasi-two-dimensional (Q2D) cuprate and iron-based (FBS) families 1 . Recently, a new family of superconducting quasi-one-dimensional (Q1D) A 2 Cr 3 As 3 (233) materials (with A = K, Cs, Rb) have proven fertile grounds for applying this general narrative to another system which has further lowereddimensionality 2,3 .The 233 family orders in non-centrosymmetric hexagonal P 6m2 space group symmetry with a structural motif of double-walled sub-nano tubes (DWS) coaxial to the caxis and of [(Cr 3 As 3 )−2 ] ∞ stoichiometry (see Fig. 1(d)) while the A-site ion acting as a spacer/charge reservoir 'layer' 2,4,5 . DFT calculations predict a Fermi surface built of complex mixtures of the Cr 3d shells with strong Q1D character 3,6,7 . Consequently, predictions of Tomonaga-Luttinger liquid (TLL)/general non-Fermiliquid (nFL) physics, Peierls distortions, ferromagnetic (FM) fluctuations/magnetic ordering and spin-triplet superconductivity have arisen creating a sea of possible ground states and interactions out of which superconductivity stabilizes.3,5,7-10 .Experimentally a similarly complex picture has emerged. nFL behaviors are observed in transport, nuclear magnetic resonance (NMR) and muon spectroscopy (µSR) measurements, which indicate significant electron correlations and strong magnetic fluctuations [11][12][13] . More exotically, measurements of the penetration depth find nodes in the superconducting gap while those of the u...

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“…Condensation of singlet pairs enables us to probe the small spin response at q = 0. In Ba(Fe,Co) 2 As 2 , finite q spin fluctuations can freeze and exhibit long range antiferromagnetism in vortex cores [50]. In FeSe we see no evidence for such behavior, which may be due to the presence of nematic order and the different contribution of orbital versus spin susceptibility.…”

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confidence: 59%

Inhomogeneous Knight shift in vortex cores of superconducting FeSe

Vinograd,

Edwards,

Wang

et al. 2021

Preprint

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We report 77 Se NMR data in the normal and superconducting states of a single crystal of FeSe for several different field orientations. The Knight shift is suppressed in the superconducting state for in-plane fields, but does not vanish at zero temperature. For fields oriented out of the plane, little or no reduction is observed below Tc. These results reflect spin-singlet pairing emerging from a nematic state with large orbital susceptibility and spin-orbit coupling. The spectra and spin-relaxation rate data reveal electronic inhomogeneity that is enhanced in the superconducting state, possibly arising from enhanced density of states in the vortex cores. Despite the spin polarization of these states, there is no evidence for antiferromagnetic fluctuations.

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Competing superconducting and magnetic order parameters and field-induced magnetism in electron-dopedBa(Fe1−xCox)2As2

Cited by 10 publications

References 71 publications

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe_2−xCo_xAs₂single crystals

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe_2−xCo_xAs₂single crystals

Coupling of structure to magnetic and superconducting orders in quasi-one-dimensional K2Cr3As3

Inhomogeneous Knight shift in vortex cores of superconducting FeSe

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Competing superconducting and magnetic order parameters and field-induced magnetism in electron-dopedBa(Fe1−xCox)2As2

Cited by 10 publications

References 71 publications

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe2−xCoxAs2single crystals

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe2−xCoxAs2single crystals

Coupling of structure to magnetic and superconducting orders in quasi-one-dimensional K2Cr3As3

Inhomogeneous Knight shift in vortex cores of superconducting FeSe

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Observation of anomalous admixture of superconducting and magnetic fractions in BaFe_2−xCo_xAs₂single crystals

Observation of anomalous admixture of superconducting and magnetic fractions in BaFe_2−xCo_xAs₂single crystals