Anisotropic fluctuations and quasiparticle excitations in FeSe_0.5Te_0.5

Abstract

We present data for the temperature dependence of the magnetic penetration depth lambda(T), heat capacity C(T), resistivity R(T) and magnetic torque ?tau for highly homogeneous single crystal samples of Fe1:0Se0:44(4)Te0:56(4). lambda(T) was measured down to 200mK in zero field. We find lambda(T) follows a power law lambda~T^n with n = 2.2 +/- 0.1. This is similar to some 122 iron-arsenides and likely results from a sign-changing pairing state combined with strong scattering. Magnetic fields of up to B =55T or 14T were used for the ? tau(B) and C(T)/R(T) measurements respectively. The specific heat, resistivity and torque measurements were used to map out the (H,T) phase diagram in this material. All three measurements were conducted on exactly the same single crystal sample so that the different information revealed by these probes is clearly distinguished. Heat capacity data strongly resemble those found for the high Tc cuprates, where strong fluctuation effects wipe-out the phase transition at Hc2. Unusually, here we find the fluctuation effects appear to be strongly anisotropic.

arXiv comment10 pages, 9 figures, submitted to PRB

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• A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)2
• Significant enhancement of upper critical fields by doping and strain in Fe-based superconductors
• Physical properties of FeSe${}_{0.5}$Te${}_{0.5}$ single crystals grown under different conditions
• Dynamics and mechanism of oxygen annealing in Fe${}_{1+y}$Te${}_{0.6}$Se${}_{0.4}$ single crystal
• Thermodynamic phase diagram of Fe(Se${}_{0.5}$Te${}_{0.5}$) single crystals up to 28 Tesla
• Quantum oscillations and upper critical magnetic field of the iron-based superconductor FeSe
• Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor
• Anisotropic magnetism, superconductivity, and the phase diagram of Rb(1-x)Fe(2-y)Se2
• Anomalous critical fields in quantum critical superconductors
• Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal
• Improvement of superconducting properties of FeSe0.5Te0.5 single crystals by Mn substitution
• 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
• Competing pairing interactions responsible for the large upper critical field in a stoichiometric iron-based superconductor, CaKFe${}_4$As${}_4$
• Thermodynamics of transition to BCS-BEC crossover superconductivity in FeSe${}_{1-x}$S${}_x$
• How robust the global measurements of London penetration depth are: the case of Fe(Te${}_{1-x}$,Se${}_x$)
• Disorder-dependent superconducting phase-diagram at high magnetic fields in Fe${}_{1+y}$Se${}_x$Te${}_{1-x}$ ($x\sim 0.4$)
• Superconducting fluctuations in isovalently-substituted BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$: Possible observation of multiband effects
• Fluctuations in two-band superconductors in a strong magnetic field
• Multi-band description of the upper critical field of bulk FeSe
• Possible nodal superconducting gap in Fe${}_{1+y}$(Te${}_{1-x}$Se${}_x$) single crystals from ultra-low temperature penetration depth measurements
• Comment on "Precision global measurements of London penetration depth in FeTe${}_{0.58}$Se${}_{0.42}$"
• Reply to "Comment on \emph{"Precision global measurements of London penetration depth in Fe(Te${}_{0.58}$Se${}_{0.42}$)"}"
• Superconducting Stiffness and Coherence Length of FeSe${}_{0.5}$Te${}_{0.5}$ Measured in Zero-Applied Field