Regensburg 2016 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 25: Superconductivity: Fe-based Superconductors - 1111 & 111
TT 25.4: Vortrag
Dienstag, 8. März 2016, 10:15–10:30, H19
Physical Properties of Off-Stoichiometric LiFeAs — •Uwe Gräfe1, Shiv Jee Singh1, Robert Beck1, Hans-Joachim Grafe1, Sabine Wurmehl1,3, Christian Hess1,2, and Bernd Büchner1,3 — 1IFW Dresden, Institut für Festkörperforschung, Postfach 270116 01171 Dresden — 2Center for Transport and Devices, TU Dresden, 01169 Dresden — 3Institut für Festkörperphysik, TU Dresden, 01062 Dresden
It is known that small modifications on the stoichiometry of LiFeAs have high impact on the physical properties in the normal and superconducting state. Here we present a systematic study on the Li-Fe-As system by XRD, NQR and resistivity. We synthesized samples with different nominal compositions of Li, Fe and As by solid state reaction and show that, besides stoichiometric LiFeAs, only enriching the system with Fe forms phase pure samples. The modifications due to this enrichment can be tracked by a shift of the NQR-frequency and the lattice constants. Thus NQR can be taken as a measure for the changes induced by additional Fe in Li-Fe-As. We further show that these changes are not only decreasing Tc but also cause a sudden reduction of normal state resistivity and electron-electron scattering. Altogether we therefore conclude that Fe has a charge doping effect on Li-Fe-As.