title: Evidence for strong-coupling s-wave superconductivity in MgB2: (11)B NMR Study.
abstract: We have investigated a gap structure in a newly discovered superconductor, MgB2, through measurement of the (11)B nuclear spin-lattice relaxation rate, (11)(1/T(1)). (11)(1/T(1)) is proportional to the temperature (T) in the normal state, and decreases exponentially in the superconducting (SC) state, revealing a tiny coherence peak just below T(c). The T dependence of 1/T(1) in the SC state can be accounted for by an s-wave SC model with a large gap size of 2Delta/k(B)T(c) approximately 5 which suggests it is in a strong-coupling regime.
authors.affiliation: Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kotegawa
authors.forename: K
authors.initials: K
authors.lastname: Ishida
authors.forename: Y
authors.initials: Y
authors.lastname: Kitaoka
authors.forename: T
authors.initials: T
authors.lastname: Muranaka
authors.forename: J
authors.initials: J
authors.lastname: Akimitsu