Seebeck effect in Fe1+xTe1-ySey single crystals

Abstract

We present measurements of resistivity and thermopower of Fe1+xTe1-ySey single crystalline samples with y=0, 0.1, 0.2, 0.3 and 0.45 in zero field and in a magnetic field B=8T. We propose a qualitative analysis of the temperature behavior of S, where the samples are described as almost compensated semimetals: different electron and hole bands with similar carrier concentrations compete and their relative contribution to the thermoelectric transport depends on the respective filling, mobility and coupling with phonons. For y>=0.2, superconductivity occurs and the optimum Se-doping level for a maximum Tc of 13 K turns out to be y=0.3. At low temperatures, evidence of a contribution to S by an excitation-drag mechanism is found, while at high temperatures a strikingly flat behavior of S is explained within a narrow band Hubbard model. The support of a theoretical background which could provide band resolved parameters such as carrier density, mobility and electron-phonon coupling of each band would allow to extract from our data valuable quantitative information on the transport and superconducting mechanisms of these iron chalcogenides.

9 pages, 3 figures

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• Observation of lattice softening at $T_{\mathrm{c}}$ in the FeSe${}_{0.5}$Te${}_{0.5}$ superconductor
• Magneto Seebeck effect in REFeAsO (RE=rare earth) compounds: probing the magnon drag scenario
• Magnetothermoelectric effects in Fe{1+d}Te{1-x}Se{x}
• Magnetic glassy phase in FeSeTe single crystals
• Bulk and surface Dirac states accompanied by two superconducting domes in FeSe-based superconductors
• Tuning across the BCS-BEC crossover in the multiband superconductor Fe${}_{1+y}$Se${}_x$Te${}_{1-x}$ : An angle-resolved photoemission study
• The uncollapsed LaFe2As2 phase: compensated, highly doped, electron-phonon coupled, iron-based superconductor
• Non-Fermi liquid transport and strong mass enhancement near the nematic quantum critical point in FeSe${}_x$Te${}_{1-x}$ thin films
• The influence of magnetic order on the magnetoresistance anisotropy of Fe${}_{1+\delta -x}$Cu${}_x$Te