FeTe${}_{0.55}$Se${}_{0.45}$: a multiband superconductor in the clean and dirty limit

Abstract

The detailed optical properties of the multiband iron-chalcogenide superconductor FeTe${}_{0.55}$Se${}_{0.45}$ have been reexamined for a large number of temperatures above and below the critical temperature $T_c=14$ K for light polarized in the a-b planes. Instead of the simple Drude model that assumes a single band, above $T_c$ the normal-state optical properties are best described by the two-Drude model that considers two separate electronic subsystems; we observe a weak response (${\omega }_{p,D;1}\simeq 3000$ cm${}^{-1}$) where the scattering rate has a strong temperature dependence ($1/{\tau }_{D,1}\simeq 32$ cm${}^{-1}$ for $T\gtrsim T_c$), and a strong response (${\omega }_{p,D;2}\simeq 14500$ cm${}^{-1}$) with a large scattering rate ($1/{\tau }_{D,2}\simeq 1720$ cm${}^{-1}$) that is essentially temperature independent. The multiband nature of this material precludes the use of the popular generalized-Drude approach commonly applied to single-band materials, implying that any structure observed in the frequency dependent scattering rate $1/\tau (\omega )$ is spurious and it cannot be used as the foundation for optical inversion techniques to determine an electron-boson spectral function ${\alpha }^{2}F(\omega )$. Below $T_c$ the optical conductivity is best described using two superconducting optical gaps of $2{\Delta }_1\simeq 45$ and $2{\Delta }_2\simeq 90$ cm${}^{-1}$ applied to the strong and weak responses, respectively. The scattering rates for these two bands are vastly different at low temperature, placing this material simultaneously in both clean and dirty limit. Interestingly, this material falls on the universal scaling line initially observed for the cuprate superconductors.

11 pages, 8 figures; minor revision

References in corpus (20)

• Superconductivity at 36 K in beta-Fe1.01Se with the compression of the interlayer separation under pressure
• Density functional study of FeS, FeSe and FeTe: Electronic structure, magnetism, phonons and superconductivity
• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
• Superconductivity in iron-based F-doped layered quaternary compound Nd[O1-xFx]FeAs
• Superconductivity close to magnetic instability in Fe(Se1-xTex)0.82
• Incommensurate magnetic order in the alpha-Fe(Te,Se) superconductor systems
• Bulk Superconductivity at 14 K in Single Crystals of Fe1+yTexSe1-x
• From (pi, 0) magnetic order to superconductivity with (pi, pi) magnetic resonance in Fe1.02(Te1-xSex)
• Control of tetrahedral coordination and superconductivity in FeSe0.5Te0.5 thin films
• Scaling of the superfluid density in high-temperature superconductors
• Unabridged phase diagram for single-phased FeSexTe1-x thin films
• Muon-spin-spectroscopy study of the penetration depth of FeTe0.5Se0.5
• Evidence for a cos(4φ) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe_{0.6}Se_{0.4} Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy
• Optical conductivity and Raman scattering of iron superconductors
• Evolution from incoherent to coherent electronic states and its implications to superconductivity in FeTe1-xSex
• Extended Drude model and role of interband transitions in the mid-infrared spectra of pnictides
• Observation of an electron band above the Fermi level in FeTe${}_{0.55}$Se${}_{0.45}$ from \emph{in-situ} surface doping
• Spectral weight transfer in strongly correlated Fe${}_{1.03}$Te
• Two-band conductivity of a FeSe${}_{0.5}$Te${}_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Cited by in corpus (8)

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• Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor ${\mathrm{FeTe}}_{0.55}{\mathrm{Se}}_{0.45}$
• Band-selective clean- and dirty-limit superconductivity with nodeless gaps in the bilayer iron-based superconductor CsCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Superuid density in overdoped cuprates: thin films versus bulk samples
• Pseudogap and Strong Pairing Induced by Incipient and Shallow Bands in the Quasi-Two-Dimensional KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Optical and photoemission investigation of structural and magnetic transitions in the iron-based superconductor Sr${}_{0.67}$Na${}_{0.33}$Fe${}_2$As${}_2$
• Studies of superconductivity of Fe chalcogenides in films grown by PLD technique
• Evolution of charge dynamics in FeSe${}_{1-x}$Te${}_x$: Effects of electronic correlations and nematicity