Spin excitation anisotropy in the paramagnetic tetragonal phase of 
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Yu, Li; Wang, Weiyi; Song, Yu; Man, Haoran; Lu, Xingye; Bourdarot, F.; Dai, Pengcheng

doi:10.1103/physrevb.96.020404

Cited by 14 publications

(40 citation statements)

References 43 publications

(86 reference statements)

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“…A possible cause for this difference is that whereas divergent longitudinal fluctuations in BaFe 2 As 2 just above T N have M a > M b ≈ M c [57], anisotropic fluctuations in the normal state of BaFe 2 As 2 -derived superconductors near optimal doping exhibit M a ≈ M c > M b [34,52]. The differing character of polarization may account for the different effects on the nematic susceptibility.…”

Section: Discussionmentioning

confidence: 92%

“…While we have linked the development of spin anisotropy with deviation from CW behavior in nematic susceptibility in iron pnictides near optimal doping, diverging longitudinal fluctuations in BaFe 2 As 2 just above T N [57] do not have the same effect on nematic susceptibility, with CW nematic susceptibility persisting down to T N [58]. A possible cause for this difference is that whereas divergent longitudinal fluctuations in BaFe 2 As 2 just above T N have M a > M b ≈ M c [57], anisotropic fluctuations in the normal state of BaFe 2 As 2 -derived superconductors near optimal doping exhibit M a ≈ M c > M b [34,52].…”

Section: Discussionmentioning

confidence: 99%

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Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

et al. 2017

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We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe 0.9785 Co 0.0215 As, with coexisting superconductivity (T c ≈ 19 K) and weak antiferromagnetic order (T N ≈ 30 K, ordered moment ≈0.02 μ B /Fe). A single spin resonance mode with intensity tracking the superconducting order parameter is observed, although energy of the mode only softens slightly upon approaching T c . Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe 0.935 Co 0.045 As but different from optimal electron-, hole-, and isovalently doped BaFe 2 As 2 compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe 0.9785 Co 0.0215 As is instead present at energies below the resonance, which becomes partially gapped below T c , similar to the situation in optimally doped YBa 2 Cu 3 O 6.9 . Our results indicate that anisotropic spin fluctuations in NaFe 1−x Co x As appear in the form of a resonance in the underdoped regime, become partially gapped below T c near optimal doping, and disappear in overdoped compounds.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

et al. 2017

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“…This suggests spin anisotropy resulting from SOC in BaFe 2 (As 0.7 P 0.3 ) 2 remains similar to a superconducting sample coexisting with static AF order [27], in contrast to Ba 0.67 K 0.33 Fe 2 As 2 in which the c-axis polarized resonance is the lowest in energy [32]. For comparison, we note that spin excitation anisotropy in BaFe 2 As 2 in the AF ordered state has M c in the lowest energy, followed by M b , and M a [29,54]. In the paramagnetic state of BaFe 2 As 2 , M a diverges around T N [54].…”

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confidence: 77%

“…For comparison, we note that spin excitation anisotropy in BaFe 2 As 2 in the AF ordered state has M c in the lowest energy, followed by M b , and M a [29,54]. In the paramagnetic state of BaFe 2 As 2 , M a diverges around T N [54]. Our observation is in line with the phase diagram of P-and K-doped BaFe 2 As 2 ; whereas stripe magnetic order with ordered moment along the a axis is observed near optimal superconductivity in BaFe 2 (As 1−x P x ) 2 [45], a double-Q phase with ordered moments along the c axis is seen near optimal superconductivity in Ba 1−x K x Fe 2 As 2 [36][37][38].…”

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confidence: 99%

Spin excitation anisotropy in the optimally isovalent-doped superconductor BaFe2(As0.7P0.3)2

Zhang

Yuan

et al. 2017

Phys. Rev. B

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We use neutron polarization analysis to study spin excitation anisotropy in the optimally isovalent-doped superconductor BaFe 2 (As 0.7 P 0.3 ) 2 (T c = 30 K). Different from optimally hole-and electron-doped BaFe 2 As 2 , where there is a clear spin excitation anisotropy in the paramagnetic tetragonal state well above T c , we find no spin excitation anisotropy for energies above 2 meV in the normal state of BaFe 2 (As 0.7 P 0.3 ) 2 . Upon entering the superconducting state, significant spin excitation anisotropy develops at the antiferromagnetic (AF) zone center Q AF = (1,0,L = odd), while the magnetic spectrum is isotropic at the zone boundary Q = (1,0,L = even). By comparing the temperature, wave vector, and polarization dependence of the spin excitation anisotropy in BaFe 2 (As 0.7 P 0.3 ) 2 and hole-doped Ba 0.67 K 0.33 Fe 2 As 2 (T c = 38 K), we conclude that such anisotropy arises from spin-orbit coupling and is associated with the nearby AF order and superconductivity. DOI: 10.1103/PhysRevB.96.180503 Spin-orbit coupling (SOC) is an interaction of an electron's spin with its motion. While the importance of SOC to the electronic properties of the 4d and 5d correlated electron materials such as Sr 2 RuO 4 and Sr 2 IrO 4 is long recognized [1,2], its relevance to the physics of the 3d correlated electron materials such as iron pnictide superconductors is much less clear. Since iron pnictide superconductors are derived from metallic parent compounds exhibiting antiferromagnetic (AF) order at T N below a tetragonal-to-orthorhombic structural transition temperature T s associated with orbital ordering and nematic phase [ Fig. 1(a)] [3][4][5][6][7], most microscopic theories for iron-based superconductors are focused on the role of spin [8][9][10], orbital [11], or nematic [7,12] fluctuations to the electron pairing and superconductivity. Although angleresolved photoemission spectroscopy (ARPES) experiments on different families of iron-based superconductors have identified the presence of SOC through observation of electronic band splitting at the Brillouin zone center (ZC) below T s [13][14][15], much is unknown concerning the role of SOC to the AF order, nematic phase, electron pairing mechanism, and superconductivity [16][17][18][19].In addition to its impact on the Fermi surface and electronic band dispersions, SOC also brings lattice anisotropies into anisotropies of magnetic fluctuations [20,21] [46][47][48][49][50][51]. Although polarized INS experiments have conclusively established the presence of SOC induced lowenergy spin excitation anisotropy near the resonance mode in different families of iron-based superconductors [23][24][25][26][27][28][29][30][31][32][33][34], the spin excitation anisotropy persists in the paramagnetic tetragonal state, and becomes isotropic at temperatures well above T N and T s [25,26,[30][31][32]. Therefore, it is still unclear how SOC is coupled to spin fluctuation anisotropy and superconductivity.To resolve this problem, we used polarized INS to study low-energy spin ...

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“…For a collinear Ising antiferromagnet with second-order (or weakly first order) magnetic phase transition, magnetic critical scattering with moments polarized along the longitudinal (parallel to the ordered moment or a-axis) direction should diverge at T N , while spin fluctuations with moments polarized transverse to the ordered moment (b-and c-axis) direction should not diverge [28][29][30][31][32] . Unpolarized 33 and polarized 34 f Temperature dependence of the static ordered magnetic moment M a and M c as determined from σ SF x;z at (1, 0, 1) and (1,0,3). The vertical error bars are estimated errors from fits-to-order parameters.…”

Section: Resultsmentioning

confidence: 99%

In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe2As2

Klemm

Tian

et al. 2020

Nat Commun

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A small in-plane external uniaxial pressure has been widely used as an effective method to acquire single domain iron pnictide BaFe2As2, which exhibits twin-domains without uniaxial strain below the tetragonal-to-orthorhombic structural (nematic) transition temperature Ts. Although it is generally assumed that such a pressure will not affect the intrinsic electronic/magnetic properties of the system, it is known to enhance the antiferromagnetic (AF) ordering temperature TN ( < Ts) and create in-plane resistivity anisotropy above Ts. Here we use neutron polarization analysis to show that such a strain on BaFe2As2 also induces a static or quasi-static out-of-plane (c-axis) AF order and its associated critical spin fluctuations near TN/Ts. Therefore, uniaxial pressure necessary to detwin single crystals of BaFe2As2 actually rotates the easy axis of the collinear AF order near TN/Ts, and such effects due to spin-orbit coupling must be taken into account to unveil the intrinsic electronic/magnetic properties of the system.

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Spin excitation anisotropy in the paramagnetic tetragonal phase of BaFe2As2

Cited by 14 publications

References 43 publications

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

Spin excitation anisotropy in the optimally isovalent-doped superconductor BaFe2(As0.7P0.3)2

In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe2As2

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