Dresden 2003 – scientific programme

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TT: Tiefe Temperaturen

TT 14: Postersitzung III (Neue u. unkonventionelle Supraleiter, Anwendungen der Supraleitung, Dünne Schichten, JJs und SQUIDs, Schwere Fermionen, Kondo-Systeme)

TT 14.10: Poster

Wednesday, March 26, 2003, 14:30–19:00, P2c

Estimates of the Critical Magnetic Fields in MgB₂ — •Dirk Manske and Karl-Heinz Bennemann — Institut fuer Theoretische Physik, Freie Universitaet Berlin

Recent measurements of the upper critical field H_c2 on MgB₂ reveal a strong anisotropy of the corresponding in-plane and out-of-plane component and a strong temperature dependence. In contrast to conventional superconductors many experiments indicate also the existence of two gaps with different size. Using simple estimates we show that one can gets H_c2^ab, H_c2^c, and the anisotropy of the smaller fields H_c1^ab, H_c1^c from the approximate two gap superconductivity with Δ₁ and Δ₂ referring to σ- and π-electronic bands. For T → 0 the σ-band dominates while close to T_c the π-band plays a more important role. Finally, we also discuss the strong temperature dependence of H_c2^ab/H_c2^c that is related to interband contributions.