title: Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe1.94Co0.06)2As2.
abstract: The superconducting transition temperature (TC) in a FeSe monolayer on SrTiO3is enhanced up to 100 K (refs ,,,). High TCis also found in bulk iron chalcogenides with similar electronic structure to that of monolayer FeSe, which suggests that higher TCmay be achieved through electron doping, pushing the Fermi surface (FS) topology towards leaving only electron pockets. Such an observation, however, has been limited to chalcogenides, and is in contrast to the iron pnictides, for which the maximum TCis achieved with both hole and electron pockets forming considerable FS nesting instability. Here, we report angle-resolved photoemission characterization revealing a monotonic increase of TCfrom 24 to 41.5 K upon surface doping on optimally doped Ba(Fe1-xCox)2As2. The doping changes the overall FS topology towards that of chalcogenides through a rigid downward band shift. Our findings suggest that higher electron doping and concomitant changes in FS topology are favourable conditions for the superconductivity, not only for iron chalcogenides, but also for iron pnictides.
authors.affiliation: Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Republic of Korea.|Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: W S
authors.initials: WS
authors.lastname: Kyung
authors.affiliation: Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Republic of Korea.|Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: S S
authors.initials: SS
authors.lastname: Huh
authors.affiliation: Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Koh
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: K-Y
authors.initials: KY
authors.lastname: Choi
authors.affiliation: Department of Physics, Osaka University 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Eisaki
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Denlinger
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: S-K
authors.identifier: http://orcid.org/0000-0003-0711-8514
authors.initials: SK
authors.lastname: Mo
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: C
authors.initials: C
authors.lastname: Kim
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea.|Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.|Department of Physics, KAIST, Daejon 34141, Republic of Korea.
authors.forename: Y K
authors.initials: YK
authors.lastname: Kim