title: Separating pairing from quantum phase coherence dynamics above the superconducting transition by femtosecond spectroscopy.
abstract: In classical superconductors an energy gap and phase coherence appear simultaneously with pairing at the transition to the superconducting state. In high-temperature superconductors, the possibility that pairing and phase coherence are distinct and independent processes has led to intense experimental search of their separate manifestations. Using femtosecond spectroscopy methods we now show that it is possible to clearly separate fluctuation dynamics of the superconducting pairing amplitude from the phase relaxation above the critical transition temperature. Empirically establishing a close correspondence between the superfluid density measured by THz spectroscopy and superconducting optical pump-probe response over a wide region of temperature, we find that in differently doped Bi(2)Sr(2)CaCu(2)O(8+δ) crystals the pairing gap amplitude monotonically extends well beyond Tc, while the phase coherence shows a pronounced power-law divergence as T → T(c), thus showing that phase coherence and gap formation are distinct processes which occur on different timescales.
authors.affiliation: Jozef Stefan Institute and International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: I
authors.initials: I
authors.lastname: Madan
authors.affiliation: Department of Physics, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kurosawa
authors.affiliation: Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Toda
authors.affiliation: Department of Physics, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Oda
authors.affiliation: Jozef Stefan Institute and International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: T
authors.initials: T
authors.lastname: Mertelj
authors.affiliation: Jozef Stefan Institute and International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: P
authors.initials: P
authors.lastname: Kusar
authors.affiliation: Jozef Stefan Institute and International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: D
authors.initials: D
authors.lastname: Mihailovic