How robust the global measurements of London penetration depth are: the case of Fe(Te${}_{1-x}$,Se${}_x$)

Abstract

We report tunnel diode resonator measurements of in-plane London penetration depth, $\lambda (T)$, in optimally-doped single crystals of Fe(Te${}_{0.58}$Se${}_{0.42}$) with $T_c\sim$ 14.8 K. Systematic measurements were carried out for six samples with different size and surface roughness. The power-law behavior, $\Delta \lambda (T)=A{T}^n$ was found for all samples with the average exponent $n_{avg}=2.3\pm 0.1$ and the pre-factor $A_{avg}=1.0\pm 0.2$ nm/K${}^{2.3}$. The average superfluid density is well described by the self-consistent two-gap $\gamma$ model resulting in ${\Delta }_{{}_I}(0)/k_B{T}_c$ = 1.93 and ${\Delta }_{{}_{II}}(0)/k_B{T}_c$ = 0.9. By analyzing the data obtained on samples of different size and deliberately introduced surface roughness, it is concluded that the calibration procedure used to obtain $\lambda (T)$ from the measured TDR frequency shift is quite robust and the uncertainty in sample dimensions and the nature of surface roughness play only minor role. The exponent $n$, directly related to the superconducting gap structure, remains virtually unchanged. The calibration - dependent pre-factor $A$ shows some variation, but stays within reasonable margin ruling out some recent suggestions that surface conditions can significantly affect the results. Our results confirm that precision global measurements provide the most objective information regarding temperature - dependent London penetration depth.

References in corpus (20)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• The superconductivity at 18 K in LiFeAs system
• Density functional study of FeS, FeSe and FeTe: Electronic structure, magnetism, phonons and superconductivity
• Superconductivity close to magnetic instability in Fe(Se1-xTex)0.82
• Tellurium substitution effect on superconductivity of the alpha-phase Iron Selenide
• Incommensurate magnetic order in the alpha-Fe(Te,Se) superconductor systems
• Bulk Superconductivity at 14 K in Single Crystals of Fe1+yTexSe1-x
• Magnetic Penetration Depth in Unconventional Superconductors
• Substitution Effects on FeSe Superconductor
• Superconductivity at 17 K in (Fe2P2)(Sr4Sc2O6): a new superconducting layered pnictide oxide with a thick perovskite oxide layer
• Spin Gap and Resonance at the Nesting Wavevector in Superconducting FeSe0.4Te0.6
• London Penetration Depth in Iron - based Superconductors
• Superfluid density and specific heat within self-consistent scheme for two-band superconductor
• (Sr_3Sc_2O_5)Fe_2As_2 as a possible parent compound for FeAs-based superconductors
• Tuning the superconducting and magnetic properties in Fe_ySe_0.25Te_0.75 by varying the Fe-content
• Evidence for Unconventional Superconductivity in Arsenic-Free Iron-Based Superconductor FeSe : A ^77Se-NMR Study
• Thermodynamic phase diagram of Fe(Se${}_{0.5}$Te${}_{0.5}$) single crystals up to 28 Tesla
• Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal
• Muon-spin-spectroscopy study of the penetration depth of FeTe0.5Se0.5
• Anisotropic fluctuations and quasiparticle excitations in FeSe_0.5Te_0.5

Cited by in corpus (9)

• Superconducting properties of sulfur-doped iron selenide
• Evolution of London penetration depth with scattering in single crystals of K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
• Unusual microwave response and bulk conductivity of very thin fese0.3te0.7 films as a function of temperature
• Possible nodal superconducting gap in Fe${}_{1+y}$(Te${}_{1-x}$Se${}_x$) single crystals from ultra-low temperature penetration depth measurements
• Direct measurement of the temperature dependence of the magnetic penetration depth in Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$ superconductors
• Comment on "Precision global measurements of London penetration depth in FeTe${}_{0.58}$Se${}_{0.42}$"
• Anisotropy of the superconducting fluctuations in multiband superconductors: the case of LiFeAs
• Superconducting Gap and Symmetry in FeSe_1-x_Te_x_ Studied by Specific Heat in Magnetic Fields
• Reply to "Comment on \emph{"Precision global measurements of London penetration depth in Fe(Te${}_{0.58}$Se${}_{0.42}$)"}"