Superconductivity and fluctuation in Ba${}_{1-p}$K${}_p$Fe${}_2$As${}_2$ and Ba(Fe${}_{1-n}$Co${}_n$)${}_2$As${}_2$

Abstract

We study the interplay of fluctuations and superconductivity in BaFe${}_2$As${}_2$ (Ba-122) compounds with Ba and Fe substituted by K ($p$ doping) and Co ($n$ doping), respectively. To this end we measured electronic Raman spectra as a function of polarisation and temperature. We observe gap excitations and fluctuations for all doping levels studied. The response from fluctuations is much stronger for Co substitution and, according to the selection rules and the temperature dependence, originates from the exchange of two critical spin fluctuations with characteristic wave vectors $(\pm \pi ,0)$ and $(0,\pm \pi )$. At 22\% K doping ($p=0.22$), we find the same selection rules and spectral shape for the fluctuations but the intensity is smaller by a factor of 5. Since there exists no nematic region above the orthorhombic spin-density-wave (SDW) phase the identification of the fluctuations via the temperature dependence is not possible. The gap excitations in the superconducting state indicate strongly anisotropic near-nodal gaps for Co substitution which make the observation of collective modes difficult. The variation with doping of the spectral weights of the $A_{1g}$ and $B_{1g}$ gap features does not support the influence of fluctuations on Cooper pairing. Therefore, the observation of Bardasis-Schrieffer modes inside the nearly clean gaps on the K-doped side remains the only experimental evidence for the relevance of fluctuations for pairing.

arXiv comment10 pages, 9 figures, accepted for publication in Phys. Status Solidi B

References in corpus (48)

• A Common Thread: the pairing interaction for the unconventional superconductors
• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• Nematic order in iron superconductors - who is in the driver's seat?
• Interfacial mode coupling as the origin of the enhancement of Tc in FeSe films on SrTiO3
• Inelastic Light Scattering From Correlated Electrons
• Orbital Fluctuation Mediated Superconductivity in Iron Pnictides: Analysis of Five Orbital Hubbard-Holstein Model
• Resonant Spin Excitation in the High Temperature Superconductor Ba0.6K0.4Fe2As2
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Enhancement of superconductivity near a nematic quantum critical point
• Competing order and nature of the pairing state in the iron pnictides
• Momentum dependence of the superconducting gap in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Structural quantum criticality and superconductivity in iron-based superconductor Ba(Fe1-xCox)2As2
• Observation of incipient charge nematicity in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Nematic susceptibility of hole- and electron-doped BaFe2As2 iron-based superconductors from shear modulus measurements
• A Systematic Study of Electron-Phonon Coupling to Oxygen Modes Across the Cuprates
• Manifestations of nematic degrees of freedom in the magnetic, elastic, and superconducting properties of the iron pnictides
• d-wave superconductivity near charge instabilities
• Electronic Raman scattering in superconductors as a probe of anisotropic electron pairing
• Carrier relaxation, pseudogap, and superconducting gap in high-Tc cuprates: A Raman scattering study
• Alternative route to charge density wave formation in multiband systems
• Charge Nematicity and Electronic Raman Scattering in Iron-based Superconductors
• Electronic nematic susceptibility of iron-based superconductors
• Interplay of magnetic and structural transitions in Fe-based pnictide superconductors
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Band and momentum dependent electron dynamics in superconducting $\mathrm{Ba}(\mathrm{F}{\mathrm{e}}_{1-\mathrm{x}}\mathrm{C}{\mathrm{o}}_{\mathrm{x}}{)}_2\mathrm{A}{\mathrm{s}}_2$ as seen via electronic Raman scattering
• Critical Quadrupole Fluctuations and Collective Modes in Iron Pnictide Superconductors
• Nematic fluctuations and the magneto-structural phase transition in $\mathrm{Ba}(\mathrm{F}{\mathrm{e}}_{1-\mathrm{x}}\mathrm{C}{\mathrm{o}}_{\mathrm{x}}{)}_2\mathrm{A}{\mathrm{s}}_2$
• Theory of Electronic Raman Scattering in Disordered $d-$wave Superconductors
• Transport properties and asymmetric scattering in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ single crystals compared to the electron doped counterparts Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$}
• Raman-Scattering Detection of Nearly Degenerate $s$-Wave and $d$-Wave Pairing Channels in Iron-Based Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ and Rb${}_{0.8}$Fe${}_{1.6}$Se${}_2$ Superconductors
• Dynamical Properties of Charged Stripes in La_{2-x}Sr_xCuO_4
• Pinpointing Gap Minima in Ba(Fe${}_{0.94}$Co${}_{0.06}{)}_2$As${}_2$ \textit{via} Band Structure Calculations and Electronic Raman Scattering
• Physical origin of the buckling in CuO${}_2$: Electron-phonon coupling and Raman spectra
• Charge-fluctuation contribution to the Raman response in superconducting cuprates
• Raman Scattering versus Infrared Conductivity: Evidence for one-dimensional Conduction in La_{2-x}Sr_{x}CuO_{4}
• Nematic resonance in the Raman response of iron-based superconductors
• Collective $d-$wave Excitonic Modes in the Fe-Superconductors
• Manifestation of nematic degrees of freedom in the Raman response function of iron pnictides
• Impact of the Spin Density Wave Order on the Superconducting Gap of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Raman scattering study of anomalous charge-, spin-, and lattice-dynamics in the charge-ordered phase of ${\mathbf{Bi}}_{1-x}{\mathbf{Ca}}_x{\mathbf{MnO}}_3$ ($x>0.5$)
• Self-energy effects and electron-phonon coupling in Fe-As superconductors
• Electronic Raman scattering from orbital nematic fluctuations
• Raman scattering as a probe of nematic correlations
• Spin nematic fluctuations near a spin-density-wave phase
• Electron-boson glue function derived from electronic Raman scattering
• Optical sum rules that relate to the potential energy of strongly correlated systems
• Optical symmetries and anisotropic transport in high-Tc superconductors
• Superconducting properties of (Ba-K)Fe2As2 single crystals disordered with fast neutron irradiation

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• Nematic Fluctuations and Phase Transitions in LaFeAsO: a Raman Scattering Study
• Fluctuations and pairing in Fe-based superconductors: Light scattering experiments
• Many-body physics-induced selection rules: application to Raman spectroscopy
• Superconducting gap and nematic resonance at the quantum critical point observed by Raman scattering in $\mathrm{BaF}{\mathrm{e}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$