title: Electronic structure and relaxation dynamics in a superconducting topological material.
abstract: Topological superconductors host new states of quantum matter which show a pairing gap in the bulk and gapless surface states providing a platform to realize Majorana fermions. Recently, alkaline-earth metal Sr intercalated Bi2Se3 has been reported to show superconductivity with a Tc ~ 3 K and a large shielding fraction. Here we report systematic normal state electronic structure studies of Sr0.06Bi2Se3 (Tc ~ 2.5 K) by performing photoemission spectroscopy. Using angle-resolved photoemission spectroscopy (ARPES), we observe a quantum well confined two-dimensional (2D) state coexisting with a topological surface state in Sr0.06Bi2Se3. Furthermore, our time-resolved ARPES reveals the relaxation dynamics showing different decay mechanism between the excited topological surface states and the two-dimensional states. Our experimental observation is understood by considering the intra-band scattering for topological surface states and an additional electron phonon scattering for the 2D states, which is responsible for the superconductivity. Our first-principles calculations agree with the more effective scattering and a shorter lifetime of the 2D states. Our results will be helpful in understanding low temperature superconducting states of these topological materials.
authors.affiliation: Condensed Matter and Magnet Science Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.|Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
authors.forename: Madhab
authors.initials: M
authors.lastname: Neupane
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Yukiaki
authors.initials: Y
authors.lastname: Ishida
authors.affiliation: Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Raman
authors.initials: R
authors.lastname: Sankar
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors.forename: Jian-Xin
authors.initials: JX
authors.lastname: Zhu
authors.affiliation: Joseph Henry Laboratory and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Sanchez
authors.affiliation: Joseph Henry Laboratory and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Ilya
authors.initials: I
authors.lastname: Belopolski
authors.affiliation: Joseph Henry Laboratory and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Su-Yang
authors.initials: SY
authors.lastname: Xu
authors.affiliation: Joseph Henry Laboratory and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Nasser
authors.initials: N
authors.lastname: Alidoust
authors.affiliation: Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
authors.forename: M Mofazzel
authors.initials: MM
authors.lastname: Hosen
authors.affiliation: ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Shik
authors.initials: S
authors.lastname: Shin
authors.affiliation: Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Fangcheng
authors.initials: F
authors.lastname: Chou
authors.affiliation: Joseph Henry Laboratory and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: M Zahid
authors.initials: MZ
authors.lastname: Hasan
authors.affiliation: Condensed Matter and Magnet Science Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Durakiewicz