Strong Correlations and Magnetic Frustration in the High<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>T</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math>Iron Pnictides

Si, Qimiao; Abrahams, Elihu

doi:10.1103/physrevlett.101.076401

Cited by 739 publications

(788 citation statements)

References 30 publications

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“…Various theories have been proposed for the pairing symmetry in the doped Fe-based oxypnictides [11,12,13,14,15,16,57,58,59,60]. As confirmed by recent ARPES measurements [52], doped Fe-based oxypnictides have hole pockets in the Brillouin zone center and electron pockets in the zone edges [51].…”

Section: Resultsmentioning

confidence: 79%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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In this article, we review our recent studies of microwave penetration depth, lower critical fields, and quasiparticle conductivity in the superconducting state of Fe-arsenide superconductors. Highsensitivity microwave surface impedance measurements of the in-plane penetration depth λ ab in single crystals of electron-doped PrFeAsO1−y (y ∼ 0.1) and hole-doped Ba1−xKxFe2As2 (x ≈ 0.55) are presented. In clean crystals of Ba1−xKxFe2As2, as well as in PrFeAsO1−y crystals, the penetration depth shows flat temperature dependence at low temperatures, indicating that the superconducting gap opens all over the Fermi surface. The temperature dependence of superfluid density λ 2 ab (0)/λ 2 ab (T ) in both systems is most consistent with the existence of two different gaps. In Ba1−xKxFe2As2, we find that the superfluid density is sensitive to degrees of disorder inherent in the crystals, implying unconventional impurity effect. We also determine the lower critical field Hc1 in PrFeAsO1−y by using an array of micro-Hall probes. The temperature dependence of Hc1 saturates at low temperatures, fully consistent with the superfluid density determined by microwave measurements. The anisotropy of Hc1 has a weak temperature dependence with smaller values than the anisotropy of upper critical fields at low temperatures, which further supports the multi-gap superconductivity in Fe-arsenide systems. The quasiparticle conductivity shows an enhancement in the superconducting state, which suggests the reduction of quasiparticle scattering rate due to the gap formation below Tc. From these results, we discuss the structure of the superconducting gap in these Fe-arsenides, in comparison with the high-Tc cuprate superconductors.

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Section: Resultsmentioning

confidence: 79%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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“…In some systems with extremely large ratio U/t, it is questioned whether this retarded scattering based picture can still be used or not. In this case, some people argue that the local super-exchange J dominates the pairing process here, leading to the simultaneous pairing [39,40] with a very strong pairing strength. One of the extreme cases is the so-called resonance-valence-bond (RVB) spin liquid state for the s = 1/2 systems, for example in the cuprates.…”

Section: T/u>>1 T/u 1 T/u<<1mentioning

confidence: 96%

Study on Unconventional Superconductivity after the BCS Paradigm

Wen

2014

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

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The Bardeen-Cooper-Schrieffer (BCS) theoretical picture has successfully explained the phenomenon of superconductivity in many single element and alloy superconductors. It suggests that the superconductivity is established through quantum condensation of vast number of Copper pairs formed by exchanging phonons between two electrons with opposite momentum and spins near the Fermi energy. This interesting paradigm has dominated the field of superconductivity since 1957. Many superconductors discovered in past three decades, such as the cuprates, iron pnictide/charcogenide and heavy Fermion superconductors seem, however, to violate the BCS picture to some extent. Most of these new superconducting systems seem to get rid of the phonons, instead use the antiferromagnetic spin fluctuations as the pairing gluons. In cuprate superconductors, the origin for the pairing may be even more exotic. In this short report, we will summarize part of these progresses and try to guide readers to possibly new schemes of superconductivity after the BCS paradigm.

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“…There is now a clear consensus that the orthorhombic phase in the iron pnictides is just such a spin-driven nematic phase, where the primary order parameter is this Ising bond order [7]. This order has been found in both local [5,6,8,9] and itinerant [10,11] models, and appears to be quite generic. Indeed, this phenomena is relevant beyond the iron pnictides, and has recently been explored above the charge density wave phase proposed in the cuprates [12,13], and in tetragonal Kondo insulators [14].…”

Section: Introductionmentioning

confidence: 99%

Emergent Ising degrees of freedom above a double-stripe magnetic ground state

Zhang

Flint

2017

Phys. Rev. B

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Double-stripe magnetism [ Q = ( π / 2 , π / 2 ) ] has been proposed as the magnetic ground state for both the iron-telluride and BaTi 2 Sb 2 O families of superconductors. Double-stripe order is captured within a J 1 − J 2 − J 3 Heisenberg model in the regime J 3 ≫ J 2 ≫ J 1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector ( π , π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one. Double-stripe magnetism [Q = (π/2,π/2)] has been proposed as the magnetic ground state for both the iron-telluride and BaTi 2 Sb 2 O families of superconductors. Double-stripe order is captured within a J 1 -J 2 -J 3 Heisenberg model in the regime J 3 J 2 J 1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π,π). Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one. Disciplines Condensed Matter Physics

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Strong Correlations and Magnetic Frustration in the HighTcIron Pnictides

Cited by 739 publications

References 30 publications

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Study on Unconventional Superconductivity after the BCS Paradigm

Emergent Ising degrees of freedom above a double-stripe magnetic ground state

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