The pairing state in KFe2As2 studied by measurements of the magnetic vortex lattice

Abstract

Understanding the mechanism and symmetry of electron pairing in iron-based superconductors represents an important challenge in condensed matter physics [1-3]. The observation of magnetic flux lines - "vortices" - in a superconductor can contribute to this issue, because the spatial variation of magnetic field reflects the pairing. Unlike many other iron pnictides, our KFe2As2 crystals have very weak vortex pinning, allowing small-angle-neutron-scattering (SANS) observations of the intrinsic vortex lattice (VL). We observe nearly isotropic hexagonal packing of vortices, without VL-symmetry transitions up to high fields along the fourfold c-axis of the crystals, indicating rather small anisotropy of the superconducting properties around this axis. This rules out gap nodes parallel to the c-axis, and thus d-wave and also anisotropic s-wave pairing [2, 3]. The strong temperature-dependence of the intensity down to T<<Tc indicates either widely different full gaps on different Fermi surface sheets, or nodal lines perpendicular to the axis.

13 pages, 3 figures

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• Weak superconducting pairing and a single isotropic energy gap in stoichiometric LiFeAs
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• Symmetry and disorder of the vitreous vortex lattice in an overdoped BaFe_{2-x}Co_xAs_2 superconductor: Indication for strong single-vortex pinning
• Fermi surface and order parameter driven vortex lattice structure transitions in twin-free YBa2Cu3O7
• Generic First Order Orientation Transition of Vortex Lattices in Type II Superconductors

Cited by in corpus (40)

• Gap symmetry and structure of Fe-based superconductors
• Functional Renormalization Group for multi-orbital Fermi Surface Instabilities
• Exotic d-wave superconductivity in strongly hole doped K(x)Ba(1-x)Fe2As2
• Crossover from weak to strong pairing in unconventional superconductors
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Specific heat and upper critical field in KFe2As2 single crystals
• Angle-resolved photoemission evidence of s-wave superconducting gap in KxFe2-ySe2 superconductor
• Gap Symmetry in KFe_2As_2 and cos 4θgap component in LiFeAs
• Energy Gap Evolution Across the Superconductivity Dome in Single Crystals of (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$
• Spin fluctuations and unconventional pairing in KFe${}_2$As${}_2$
• Potential antiferromagnetic fluctuations in hole-doped iron-pnictide superconductor Ba_{1-x}K_{x}Fe_{2}As_{2} studied by ^{75}As nuclear magnetic
• Evidence for exclusion of the possibility of $d$-wave superconducting-gap symmetry in Ba-doped KFe${}_2$As${}_2$
• Magnon radiation by moving Abrikosov vortices in ferromagnetic superconductors and superconductor-ferromagnet multilayers
• Multiband Superconductivity in KFe2As2: Evidence for one Isotropic and several Liliputian Energy Gaps
• Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Upper critical field of high quality single crystals of KFe${}_2$As${}_2$
• Upper critical field of isoelectron substituted SrFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Magnetic-field-induced nonlocal effects on the vortex interactions in twin-free YBa2Cu3O7
• Evolution of London penetration depth with scattering in single crystals of K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
• A 17 T horizontal field cryomagnet with rapid sample change designed for beamline use
• Rotation of the magnetic vortex lattice in Ru7B3 driven by the effects of broken time-reversal and inversion symmetry
• Anisotropy and multiband superconductivity in Sr2RuO4
• Simultaneous Evidence for Pauli Paramagnetic Effects and Multiband Superconductivity in KFe${}_2$As${}_2$ by Small-Angle Neutron Scattering Studies of the Vortex Lattice
• Pressure dependence of coherence-incoherence crossover behavior in KFe2As2 observed by resistivity and 75As-NMR/NQR
• Evolution of quasiparticle excitations with critical mass enhancement in superconducting AFe2As2 (A = K, Rb, and Cs)
• Sub-micrometer resolution neutron tomography
• Cyclotron resonance and mass enhancement by electron correlation in KFe${}_2$As${}_2$
• Vortex lattice structure in BaFe2(As0.67P0.33)2 by the small-angle neutron scattering technique
• Pairing Symmetry in Iron-Pnictide Superconductor KFe${}_2$As${}_2$
• Eilenberger theory and London theory for transverse components of flux line lattice form factors in uniaxial superconductors
• Observation of the Non-linear Meissner Effect
• SANS Study of Vortex Lattice Structural Transition in Optimally Doped (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$
• Elastic contribution to interaction of vortices in uniaxial superconductors
• Vortex lattice and vortex bound states in CsFe${}_2$As${}_2$ investigated by scanning tunneling microscopy/spectroscopy
• Singlet-triplet mixing in the order parameter of the noncentrosymmetric superconductor Ru${}_7$B${}_3$
• Orbital and Pauli limiting effects in heavily doped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Bulk domain Meissner state in the ferromagnetic superconductor EuFe${}_2$(As${}_{0.8}$P${}_{0.2}$)${}_2$: Consequence of compromise between ferromagnetism and superconductivity
• Adherence of the rotating vortex lattice in the noncentrosymmetric superconductor Ru${}_7$B${}_3$ to the London model
• Evolution of superconducting gap anisotropy in hole-doped 122 iron pnictides
• Unconventional superconductivity in the nickel-chalcogenide superconductor, TlNi${}_2$Se${}_2$