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Open Access Publications from the University of California

Electronic structure and relaxation dynamics in a superconducting topological material.

  • Author(s): Neupane, Madhab;
  • Ishida, Yukiaki;
  • Sankar, Raman;
  • Zhu, Jian-Xin;
  • Sanchez, Daniel S;
  • Belopolski, Ilya;
  • Xu, Su-Yang;
  • Alidoust, Nasser;
  • Hosen, M Mofazzel;
  • Shin, Shik;
  • Chou, Fangcheng;
  • Hasan, M Zahid;
  • Durakiewicz, Tomasz
  • et al.

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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.

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