Neutron Scattering Studies of spin excitations in hole-doped Ba0.67K0.33Fe2As2 superconductor

Zhang, Chenglin; Wang, Meng; Luo, Huiqian; Wang, Miaoyin; Liu, Mengshu; Zhao, Jun; Abernathy, D. L.; Maier, Thomas; Marty, Karol; Lumsden, M. D.; Chi, Songxue; Chang, S.; Rodríguez-Rivera, J. A.; Lynn, J. W.; Xiang, Tao; Hu, Jiangping; Dai, Pengcheng

doi:10.1038/srep00115

Cited by 81 publications

(70 citation statements)

References 43 publications

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“…Recent neutron scattering experiment on the same batch of Ba 0.67 K 0.33 Fe 2 As 2 crystal revealed that the low-energy spin excitations below T c displays a sinusoidal modulation, indicating clear gap at momentum transfer q z =0 but gapless behavior at q z =π. 8 Presence of nodes in different regions of FSs was also suggested in theoretical studies, including nodes on 2D electron type FSs near the zone corner 31 , vertical and small segment nodal lines on the 3D hole FS and horizontal nodes on the 3D FS 32 . As we elaborated above, the c-axis optical measurement mainly probes the 3D FS, while the nodes on the 2D electron FSs would have strong effect on the in-plane conductivity.…”

Section: Resultsmentioning

confidence: 99%

Three-dimensionality of band structure and a large residual quasiparticle population in Ba0.67K0.33<

et al. 2011

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Section: Resultsmentioning

confidence: 99%

Three-dimensionality of band structure and a large residual quasiparticle population in Ba0.67K0.33<

et al. 2011

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“…The BFA and BKFA samples used in our RIXS experiments are single crystals grown using the self-flux method 22,23 . Resistivity and bulk magnetic susceptibility measurements demonstrate the high quality of all samples (see Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The high-quality single crystals of BFA and BKFA used in the current study were grown by the flux method as described in Chen et al 22 and Zhang et al 23 High-resolution RIXS experiments were performed using the SAXES spectrometer at the Advanced Resonant Spectroscopy (ADRESS) beamline of the Swiss Light Source, Paul Scherrer Institut, Switzerland. The energy and momentum resolutions were 40 meV (HWHM) and 0.01 Å À 1 , respectively.…”

Section: Methodsmentioning

confidence: 99%

Persistent high-energy spin excitations in iron-pnictide superconductors

et al. 2013

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Motivated by the premise that superconductivity in iron-based superconductors is unconventional and mediated by spin fluctuations, an intense research effort has been focused on characterizing the spin-excitation spectrum in the magnetically ordered parent phases of the Fe pnictides and chalcogenides. For these undoped materials, it is well established that the spin-excitation spectrum consists of sharp, highly dispersive magnons. The fate of these highenergy magnetic modes upon sizable doping with holes is hitherto unresolved. Here we demonstrate, using resonant inelastic X-ray scattering, that optimally hole-doped superconducting Ba 0.6 K 0.4 Fe 2 As 2 retains well-defined, dispersive high-energy modes of magnetic origin. These paramagnon modes are softer than, though as intense as, the magnons of undoped antiferromagnetic BaFe 2 As 2 . The persistence of spin excitations well into the superconducting phase suggests that the spin fluctuations in Fe-pnictide superconductors originate from a distinctly correlated spin state. This connects Fe pnictides to cuprates, for which, in spite of fundamental electronic structure differences, similar paramagnons are present.

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“…the anisotropy is opposite and J 1 is AFM for the iron-based compounds. It is interesting to note that the spin fluctuation anisotropy is predicted to become negative (η < 0) in hole-doped AFe 2 As 2 [16], which has subsequently been observed in Ba 1−x K x Fe 2 As 2 [17].…”

Section: Figures 1(a) -(E)mentioning

confidence: 99%

Stripe Antiferromagnetic Spin Fluctuations inSrCo2As2

et al. 2013

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Inelastic neutron scattering measurements of paramagnetic SrCo2As2 at T = 5 K reveal antiferromagnetic (AFM) spin fluctuations that are peaked at a wavevector of Q AFM = (1/2, 1/2, 1) and possess a large energy scale. These stripe spin fluctuations are similar to those found in AFe2As2 compounds, where spin-density wave AFM is driven by Fermi surface nesting between electron and hole pockets separated by Q AFM . SrCo2As2 has a more complex Fermi surface and band structure calculations indicate a potential instability towards either a ferromagnetic or stripe AFM ground state. The results suggest that stripe AFM magnetism is a general feature of both iron and cobaltbased arsenides and the search for spin fluctuation-induced unconventional superconductivity should be expanded to include cobalt-based compounds.The AFe 2 As 2 compounds (A = Ca, Sr, Ba) are itinerant antiferromagnets (AFMs) where spin-density wave ordering is driven by Fermi surface nesting between electron and hole pockets [1]. The in-plane nesting vector Q AFM = (1/2, 1/2) describes a stripe AFM structure consisting of ferromagnetic (FM) chains of spins extending along the [1,1] direction with AFM alignment along [1, 1] [see Fig. 1(f)]. In Ba(Fe 1−x Co x ) 2 As 2 , electrondoping by the substitution of Co for Fe destabilizes the stripe AFM ordering by shrinking (enlarging) the hole (electron) pockets and detuning the nesting condition. Ultimately, the suppression of stripe AFM ordering upon Co substitutions of a few percent allows a superconducting ground state to appear in the presence of substantial spin fluctuations at Q AFM . Further Co substitutions (x > 12%) lead to a complete suppression of both stripe spin fluctuations [2,3] and superconductivity [4][5][6].The ACo 2 As 2 compounds with a full replacement of Fe by Co have garnered little attention. Initial experiments on BaCo 2 As 2 [7] and SrCo 2 As 2 [8] describe these materials as metals with enhanced paramagnetic susceptibility and no magnetic ordering or superconductivity down to 2 K. Band structure calculations find a large density-ofstates at the Fermi energy that is proposed to drive a ferromagnetic instability and enhanced paramagnetism [7,8]. Recent angle-resolved photoemission spectroscopy (ARPES) data on BaCo 2 As 2 [9, 10] and SrCo 2 As 2 [8] reveal a complex multi-band Fermi surface and, unlike the iron arsenides, no clear nesting features exist that might suggest an instability towards AFM ordering.In this Letter, we report the remarkable discovery that SrCo 2 As 2 is near an instability to stripe AFM order, not ferromagnetism, i.e. it adopts the same magnetic state as found in the tetragonal phase of iron arsenide-based parent and superconducting compounds. Inelastic neutron scattering (INS) was used to measure steeply dispersing and quasi-two-dimensional (2-D) paramagnetic excitations near Q AFM = (1/2, 1/2, 1) that share many similarities to AFe 2 As 2 , despite their dissimilar Fermi surface topologies. One notable difference is the opposite anisotropy of the longitudinal a...

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Neutron Scattering Studies of spin excitations in hole-doped Ba0.67K0.33Fe2As2 superconductor

Cited by 81 publications

References 43 publications

Three-dimensionality of band structure and a large residual quasiparticle population in Ba0.67K0.33<

Three-dimensionality of band structure and a large residual quasiparticle population in Ba0.67K0.33<

Persistent high-energy spin excitations in iron-pnictide superconductors

Stripe Antiferromagnetic Spin Fluctuations inSrCo2As2

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