Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: SC: Fabrication and Characterization of Iron-Based and Other Superconductors
TT 20.2: Vortrag
Mittwoch, 24. März 2010, 09:45–10:00, H19
Metal-semiconductor transition and phase separation in superconducting Fe1+yTe1−xSex single crystals — •Sahana Roessler1, Dona Cherian2, Sasidharan Harikrishnan2, Handadi L Bhat2, Suja Elizabeth1, Frank Steglich1, Steffen Wirth1, and Liu Hao Tjeng1 — 1Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany — 2Department of Physics, Indian Institute of Science, C V Raman Avenue, Bangalore - 560012, India
We have investigated the influence of excess Fe on the electrical transport and magnetism of Fe1+yTe1−xSex (y = 0.26, 0.15, 0.12 and x =0.32, 0.34, 0.36, respectively) single crystals. All three samples exhibit superconducting transitions with critical temperatures Tc (onset) ∼ 15 K in the resistivity measurements. It has been inferred from the width of the superconducting transition and the magnitude of the lower critical field Hc1, that excess Fe occupying interstitial sites in the chalcogen planes suppresses superconductivity. Further, the temperature dependence of resistivity in the normal state changes from metallic to semiconducting behavior with increasing Fe. From the dc-magnetization, linear and non-linear response of the ac-susceptibility, we show that the superconducting state for these compositions is inhomogeneous. A possible origin of this phase separation is due to a magnetic coupling between Fe in the chalcogen planes with those in the Fe-square lattice.