Regensburg 2002 – scientific programme

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TT: Tiefe Temperaturen

TT 7: Postersitzung I: Anwendungen der Supraleitung (1-6), Dünne Schichten, Josephsonkontakte, SQUIDs (7-17), Neue und unkonv. Supraleiter(18-23), Amorphe- und Tunnelsyst. (24-28), Quantenflüssigkeiten (29-30), Syst. korr. Elektr.: Theorie I (31-45)

TT 7.23: Poster

Monday, March 11, 2002, 14:30–18:00, A

Evidence for quasi-two-dimensional superconductivity in MgB₂ — •Anatoli Sidorenko^1,2, Valerii Ryazanov³, Anna Rossolenko³, Lenar Tagirov^1,4, Christian Helbig¹, Matthias Klemm¹, Sergei Grigoriev¹, and Reinhard Tidecks¹ — ¹Institut für Physik, Universität Augsburg, D-86159 Augsburg — ²Institute of Applied Physics, MD-2028 Kishinev, Moldova — ³Institute of Solid State Physics, RU-142432 Chernogolovka — ⁴Kazan State University, RU-420008 Kazan, Russia

The crystal structure of MgB₂ and band structure calculations suggest that boron planes with quasi-two-dimensional (2D) behavior are mainly responsible for the charge transport. The superconducting properties of magnesium diboride are expected to reflect this 2D character.

We report on critical field and resistance measurements of 30 nm thick MgB₂ films grown on MgO single crystalline substrate by DC magnetron sputtering. The linear temperature dependence of the parallel and perpendicular upper critical fields revealed 3D character of magnetic field penetration into the sample. In contrast, resistivity measurements yield a temperature dependence of the fluctuation conductivity above T_c, which agrees with the Aslamazov-Larkin theory for a 2D superconductor. This experimental result indicates a quasi-two-dimensional origin of the nucleation of superconductivity in MgB₂.

This work was partially supported by INTAS Grant No. 99-00585.