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.
@article{arxiv.1511.00278,
title = {Electronic structure and relaxation dynamics in a superconducting topological material},
author = {Madhab Neupane and Yukiaki Ishida and Raman Sankar and Jian-Xin Zhu and Daniel S. Sanchez and Ilya Belopolski and Su-Yang Xu and Nasser Alidoust and Shik Shin and Fangcheng Chou and M. Zahid Hasan and Tomasz Durakiewicz},
journal= {arXiv preprint arXiv:1511.00278},
year = {2016}
}