Dresden 2009 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 36: Focussed Session: Superconductivity and Magnetism in Ferropnictides and Related Materials

TT 36.1: Topical Talk

Donnerstag, 26. März 2009, 09:30–10:00, HSZ 03

Superconductivity and Magnetism in LaO_1−xF_xFeAs — •Bernd Buechner¹, Hans-Joachim Grafe¹, Christian Hess¹, Ruediger Klingeler¹, Guenter Behr¹, Agnieszka Kondrat¹, Norman Leps¹, Guillaume Lang¹, Hans-Henning Klauss², and Hubertus Luetkens³ — ¹IFW Dresden — ²TU Dresden — ³PSI Villigen

Measuring NMR as well as muSR, transport and thermodynamic properties we have determined the phase diagram of LaO_1−xF_xFeAs superconductors. In my talk, I will show experimental studies of the magnetic ordering, properties of the superconducting state and the normal state properties in the superconducting regions of the phase diagram. While the temperature dependence of the London penetration as determined from *SR points to an isotropic s wave state, our early NMR data suggest singlet pairing and nodes of the order parameter. In the paramagnetic normal state, NMR on all three nuclei shows that the local electronic susceptibility rises with increasing temperature. This had led to suggest the presence of a pseudogap, which I will discuss in detail. The scaling of all NMR shifts with respect to the macroscopic susceptibility indicates that there is no apparent multiband effect through preferential hyperfine couplings. Relaxation measurements indicate a similar temperature-dependence for (T₁T)⁻¹, and suggest that the dynamical susceptibility changes uniformly in q space with varying temperature. The transport properties show some striking similarities to the findings in cuprates and, finally, susceptibility as well as NMR studies point to the antiferromagnetic fluctuations.