title: Pair-breaking and superconducting state recovery dynamics in MgB2.
abstract: We present studies of the photoexcited quasiparticle dynamics in MgB2 where, using femtosecond optical techniques, Cooper pair-breaking dynamics (PBD) have been temporally resolved for the first time. The PBD are strongly temperature and photoexcitation intensity dependent. Analysis of the PBD using the Rothwarf-Taylor equations suggests that the anomalous PBD arises from the fact that in MgB2 photoexcitation is initially followed by energy relaxation to high frequency phonons instead of, as commonly assumed, e-e thermalization. Furthermore, the bare quasiparticle recombination rate and the probability for pair breaking by phonons have been determined.
authors.affiliation: Los Alamos National Laboratory, MST-10, Los Alamos, New Mexico 87545, USA.
authors.forename: J
authors.initials: J
authors.lastname: Demsar
authors.forename: R D
authors.initials: RD
authors.lastname: Averitt
authors.forename: A J
authors.initials: AJ
authors.lastname: Taylor
authors.forename: V V
authors.initials: VV
authors.lastname: Kabanov
authors.forename: W N
authors.initials: WN
authors.lastname: Kang
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: E M
authors.initials: EM
authors.lastname: Choi
authors.forename: S I
authors.initials: SI
authors.lastname: Lee