Momentum Dependence Of The Superconducting Gap In Ba_(1-x)k_xfe_2as_2

摘要

The precise momentum dependence of the superconducting gap in the iron-arsenide superconductor Ba_(1-x)K_xFe_2As_2 (BKFA) with T_c=32 K was determined from angle-resolved photoemission spectroscopy (ARPES) via fitting the distribution of the quasiparticle density to a model. The model incorporates finite lifetime and experimental resolution effects, as well as accounts for peculiarities of BKFA electronic structure. We have found that the value of the superconducting gap is practically the same for the inner Γ barrel, X pocket, and "blade" pocket, and equals 9 me V, while the gap on the outer Γ barrel is estimated to be less than 4 meV, resulting in 2△/k_BT_c=6.8 for the large gap and 2△/k_BT_c<3 for the small gap. A large (77±3 %) nonsuperconducting component in the photoemission signal is observed below T_c. Details of gap extraction from ARPES data are discussed in Appendixes A and B.