Regensburg 2002 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Postersitzung II: Mesoskopische Systeme (1-19), Supraleiter: Theorie (20-26), Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter (27-33), Schwere Fermionen, Kondo-Systeme (34-45)

TT 17.24: Poster

Mittwoch, 13. März 2002, 14:30–18:00, A

Theory for phonon-induced superconductivity in MgB₂ — •Christian Joas, Ilya Eremin, Dirk Manske, and Karl Bennemann — Institut für Theoretische Physik, Freie Universität Berlin, D-14195 Berlin

We analyze superonductivity in MgB₂ observed below T_c=39 K resulting from electron-phonon coupling involving a mode at ℏ ω₁ = 24 meV and most importantly the in-plane B-B E_2g vibration at ℏ ω₂=67 meV. The quasiparticles in the boron planes originating from π- and σ-states couple strongly to the low-frequency mode and the E_2g-vibrations respectively. Using two-band Eliashberg theory, λ_π = 1.4 and λ_σ = 0.7, we calculate the gap functions Δⁱ(ω,0) (i=π, σ) and determine µ_π^⋆ = 0.1 and µ_σ^⋆ = 0.18. Our results provide an explanation of recent tunneling experiments. We get H_c2^ab/H_c2^c ≈ 4.