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.

17 pages, 3 figures

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• Time-resolved photoemission apparatus achieving sub-20-meV energy resolution and high stability
• Electronic structure of a superconducting topological insulator Sr-doped Bi2Se3

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• A comprehensive review on topological superconducting materials and interfaces
• Structural distortion behind the nematic superconductivity in Sr${}_x$Bi${}_2$Se${}_3$
• Drive the Dirac Electrons into Cooper Pairs in SrxBi2Se3
• Pressure induced re-emergence of superconductivity in superconducting topological insulator Sr0.065Bi2Se3
• Dirac State in a Centrosymmetric Superconductor alpha-PdBi2
• Muon spin rotation study of the topological superconductor SrxBi2Se3
• Nematic superconductivity in topological insulators induced by hexagonal warping
• Observability of superconductivity in Sr-doped Bi2Se3 at the surface using scanning tunneling microscope
• Quasiparticle interference in doped topological insulators with nematic superconductivity
• Full superconducting gap in the candidate topological superconductor In${}_{1-x}$Pb${}_x$Te for x = 0.2
• Low-Energy Surface States in the Normal State of $\alpha$-PdBi2 Superconductor