Multiband thermal transport in the iron-based superconductor Ba1−xKxFe2As2

Abstract

We present results of precise measurements of the thermal and electrical transport in the optimally and overdoped Ba1−xKxFe2As2 single crystals (x=0.35,0.55,0.88) and compare them to the previously reported data on Ba(Fe1−yCoy)2As2. A contraction of the electron pocket is observed upon substitution potassium for barium, but even at the extreme doping (x=0.88) there is still a noticeable contribution from negative charge carriers to the electronic transport. The size of the electron pocket in all K-doped samples is small enough to cause a significant enhancement of the respective Hall-Lorenz number. Another observed characteristic is the emergence of a maximum in the transverse thermal conductivity below the superconducting critical temperature of the optimally (x=0.35) and slightly overdoped (x=0.55) samples. The evolution of this anomaly from the optimally electron-doped Ba(Fe0.94Co0.06)2As2 to hole-overdoped Ba0.45K0.55Fe2As2 suggests formation of a uniform superconducting gap on the electron pocket in the former and regions of a depressed gap on the hole pocket in the latter.

Source-reported materials — not catalogue approval

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