Anomalous phonon behavior in superconducting 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>CaKFe</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>
: An optical study

Yang, Run; Dai, Y. M.; Xu, Bing; Zhang, Wei; Qiu, Ziyang; Sui, Qiangtao; Homes, C. C.; Qiu, Xianggang

doi:10.1103/physrevb.95.064506

Cited by 35 publications

(30 citation statements)

References 44 publications

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“…22,23) This multiband nature implies multi-gap superconductivity in CaKFe 4 As 4 . Two superconducting gaps which are nodeless and isotropic were, indeed, observed by scanning tunneling microscopy, 20) optical conductivity, 24) penetration depth, 21) muon spin rota- * k iida@cross.or.jp tion, 18) and 75 As nuclear magnetic resonance (NMR) 25) measurements. The largest superconducting gaps (∆ hole = 13 meV and ∆ electron = 12 meV) for quasi-two-dimensional hole and electron pockets that have similar diameters at the Γ and M points were reported by ARPES studies, 22) suggesting that the ideal nesting condition with the (π, π) wave vector referred to the tetragonal reciprocal lattice.…”

Section: -9)mentioning

confidence: 88%

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe₄As₄

et al. 2017

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The dynamical spin susceptibility in the new-structure-type iron-based superconductor CaKFe 4 As 4 was investigated by using a combination of inelastic neutron scattering (INS) measurements and random phase approximation (RPA) calculations. Powder INS measurements show that the spin resonance at Q res = 1.17(1) Å −1 , corresponding to the (π, π) nesting wave vector in tetragonal notation, evolves below T c . The characteristic energy of the spin resonance E res = 12.5 meV is smaller than twice the size of the superconducting gap (2∆). The broad energy feature of the dynamical susceptibility of the spin resonance can be explained by the RPA calculations, in which the different superconducting gaps on different Fermi surfaces are taken into account. Our INS and PRA studies demonstrate that the superconducting pairing nature in CaKFe 4 As 4 is the s ± symmetry.Various iron-based superconducting materials with different crystal structures have been investigated to transcend our understanding of the nature of their pairing mechanism, [1][2][3][4] as the crystal structure is believed to have a strong relationship with the superconducting transition temperature T c . 5,6) Recently, new-structure-type iron-based superconducting materials AeAFe 4 As 4 (where Ae = Ca, Sr, or Eu and A = K, Rb, or Cs) were reported. 7-9)The AeAFe 4 As 4 family exhibits T c = 32-37 K, which is relatively high compared with other stoichiometric iron-based superconductors. [10][11][12][13][14] As Ae and A layers stack alternatively between Fe 2 As 2 layers owing to the large difference between their ionic radii, AeAFe 4 As 4 belongs to the P4/mmm space group, which is different from I4/mmm in hole-doped (Ba 1−x K x )Fe 2 As 2 systems. 7, 15) AeAFe 4 As 4 has high T c at stochiometric composition and a unique crystal structure, providing us with a great opportunity to theoretically and experimentally investigate iron-based superconductivity in the absence of substitutional disorder.CaKFe 4 As 4 undergoes superconductivity below T c ≃ 35 K without other phase transitions for 1.8 ≤ T ≤ 300 K. [15][16][17] The magnetic ground state of the normal state in CaKFe 4 As 4 is paramagnetic. 16,18) Various measurements 15,16,[18][19][20][21] indicated that CaKFe 4 As 4 shows behaviors similar to optimally or slightly overdoped (Ba 1−x K x )Fe 2 As 2 . Angle-resolved photoemission spectroscopy (ARPES) measurements supported by density functional theory calculations indicated that the Fermi surface consists of three-hole pockets at the Γ point and two electron pockets at the M point. 22,23) This multiband nature implies multi-gap superconductivity in CaKFe 4 As 4 . Two superconducting gaps which are nodeless and isotropic were, indeed, observed by scanning tunneling microscopy, 20) optical conductivity, 24) penetration depth, 21) muon spin rota- * k iida@cross.or.jp tion, 18) and 75 As nuclear magnetic resonance (NMR) 25) measurements. The largest superconducting gaps (∆ hole = 13 meV and ∆ electron = 12 meV) for quasi-two-dimensional hole and electron p...

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Section: -9)mentioning

confidence: 88%

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe₄As₄

et al. 2017

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“…Thus, the presence of the few stoichiometric FeSCs offers a unique opportunity to study the phenomenon of superconductivity in these compounds with much higher accuracy both experimentally and theoretically. Among them the recently discovered CaKFe 4 As 4 (CaK1144) shows a particularly high value of the superconducting transition temperature T c ≈ 35.8 K and the upper critical field H c c2 ≈ 71 T [5][6][7][8][9][10]. At the same time if one considers the equal ratio of Ca and K in CaKFe 4 As 4 one could compare this system with hole-doped Ba 0.46 K 0.54 Fe 2 As 2 , which has a similar T c of 34 K [11,12] but is randomly disordered on the single (Ba/K) site.…”

Section: Introductionmentioning

confidence: 99%

Electronic properties, low-energy Hamiltonian, and superconducting instabilities in CaKFe4As4

et al. 2017

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We analyze the electronic properties of the recently discovered stoichiometric superconductor CaKFe4As4 by combining an ab initio approach and a projection of the band structure to a lowenergy tight-binding Hamiltonian, based on the maximally localized Wannier orbitals of the 3d Fe states. We identify the key symmetries as well as differences and similarities in the electronic structure between CaKFe4As4 and the parent systems CaFe2As2 and KFe2As2. In particular, we find CaKFe4As4 to have a significantly more quasi-two-dimensional electronic structure than the latter systems. Finally, we study the superconducting instabilities in CaKFe4As4 by employing the leading angular harmonics approximation (LAHA) and find two potential A1g-symmetry representation of the superconducting gap to be the dominant instabilities in this system.

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“…However, the peaks around 200 and 700 cm -1 in the hole-doped Ca 8.5 Na 1.5 (Pt 3 As 8 )(Fe 2 As 2 ) 5 sample appear clearly with a narrower width than those in La-underdoped Ca1038 sample, which may be due to the narrowing of the Fe-3d electron band mentioned above. The two Drude components in the fitting indicate the presence of multiple bands, as in many IBS compounds [27][28][29][30][31][32] . The temperature dependences of the plasma frequency and scattering rate of each band are shown in Figs.…”

Section: Resultsmentioning

confidence: 99%

Optical Properties in The Hole-Doped Ca8.5Na1.5(Pt3As8)(Fe2As2)5 Single Crystal

Choi

Seo

Kimura

et al. 2021

Preprint

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For newly synthesized hole-doped Ca8.5Na1.5(Pt3As8)(Fe2As2)5 single crystals, we measured the infrared reflectivity spectrum and the magnetic field dependence of magnetoresistivity and Hall resistivity. The results of these two experiments in normal states are well described by two band models. In the normal state below 150 K, the optical conductivity spectrum shows a transfer of spectral weights from the mid-infrared region to the near-infrared region. Meanwhile, the magnetoresistance and Hall resistance show a significant decrease in carrier density at 150 K. These two phenomena are due to the conversion of itinerant electrons to heavy electrons by the strong correlation effect, Hund's coupling. In the superconducting state, the spectral weight in the low frequency region by the superconducting condensate is completely suppressed, which is well analyzed by the generalized Mattis-Bardeen (M-B) model with a two superconducting gap.

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Anomalous phonon behavior in superconducting CaKFe4As4 : An optical study

Cited by 35 publications

References 44 publications

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe₄As₄

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe₄As₄

Electronic properties, low-energy Hamiltonian, and superconducting instabilities in CaKFe4As4

Optical Properties in The Hole-Doped Ca8.5Na1.5(Pt3As8)(Fe2As2)5 Single Crystal

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Anomalous phonon behavior in superconducting CaKFe4As4 : An optical study

Cited by 35 publications

References 44 publications

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4

Electronic properties, low-energy Hamiltonian, and superconducting instabilities in CaKFe4As4

Optical Properties in The Hole-Doped Ca8.5Na1.5(Pt3As8)(Fe2As2)5 Single Crystal

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Product

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Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe₄As₄

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe₄As₄