Regensburg 2010 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 34: SC: Iron-Based Superconductors - 122

TT 34.12: Vortrag

Donnerstag, 25. März 2010, 17:00–17:15, H20

Point-contact spectroscopy on doped and undoped 122 barium iron pnictides in the normal-conducting state — •Oliver Berg¹, Michael Marz¹, Thomas Wolf², Hilbert v. Löhneysen^1,2, and Gernot Goll¹ — ¹Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe — ²Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe

Point-contact spectroscopy (PCS) measurements in the superconducting state of K- and Co-doped BaFe₂As₂ single crystals exhibit, in addition to features due to superconductivity, an unexpected, weakly temperature-dependent voltage-dependence of the differential conductance dI/dV in both the superconducting and in normal states. To clarify the origin of this behavior we have investigated PCS of doped and undoped Ba-122 single crystals up to T=200 K. In additon to this ubiquitous voltage dependence, undoped BaFe₂As₂ crystals reveal a significant zero anomaly (ZBA) of the differential conductance that is common to antiferromagnetic materials. Our observation that the ZBA is absent in the doped, i. e., superconducting samples supports this assignment because doping of BaFe₂As₂ with K or Co is known to suppress the antiferromagnetic ordering. The spectra can be described with two Lorentzian functions for the the different contributions. These doped samples (Ba_0.68K_0.32Fe₂As₂ and Ba(Fe_0.935Co_0.065)₂As₂) exhbit at T < T_c the dI/dV spectra expected of Andreev reflection for two-band superconductors.