Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 20: SC: Fabrication and Characterization of Iron-Based and Other Superconductors

TT 20.12: Talk

Wednesday, March 24, 2010, 12:30–12:45, H19

Effect of Gallium Doping on Superconductivity in Germanium — •R. Skrotzki¹, T. Herrmannsdörfer¹, V. Heera², O. Ignatchik¹, M. Uhlarz¹, A. Mücklich², M. Posselt², H. Reuther², B. Schmidt², K.-H. Heinig², W. Skorupa², M. Voelskow², C. Wündisch², J. Fiedler², M. Helm², and J. Wosnitza¹ — ¹Hochfeld-Magnetlabor Dresden, Forschungszentrum Dresden-Rossendorf (FZD) — ²Institut für Ionenstrahlphysik und Materialforschung, FZD

We report recent discoveries of superconductivity in Ga-doped germanium fabricated by ion implantation and subsequent flash-lamp or oven annealing. Tuning the preparation parameters allows for varying both charge-carrier and Ga concentration in the resulting roughly 100 nm thin nano- or single-crystalline layers. Transport measurements on systematically prepared samples reveal that besides a needed charge-carrier concentration of more than 0.4 atom%, superconductivity occurs to be sensitive on the implanted Ga content which may also be attributed to a change in the phonon properties. Onset transition temperatures up to 1.4 K have been found for almost 10 atom% Ga. Further, we observe in-plane critical fields exceeding 1 T and being close to the Pauli-Clogston limit. An exceptionally low Cooper-pair density of around 10¹⁵ cm⁻³ turns out the extreme type-II character of superconductivity. Finally, our work adds to our previous report [1] and may help to understand superconductivity in doped elemental semiconductors in general.
T. Herrmannsdoerfer et. al., Phys. Rev. Lett. 102, 1027003 (2009)