Electronic structure and relaxation dynamics in a superconducting topological material

TL;DR

This study investigates the electronic structure and relaxation dynamics of Sr0.06Bi2Se3, a topological superconductor, revealing coexisting 2D and surface states with distinct decay mechanisms, advancing understanding of superconductivity in topological materials.

Contribution

The paper provides the first systematic ARPES analysis of Sr0.06Bi2Se3, identifying coexisting 2D and topological surface states and their distinct relaxation dynamics, supported by first-principles calculations.

Findings

Coexistence of 2D states and topological surface states in Sr0.06Bi2Se3.

Different decay mechanisms for surface and 2D states observed via time-resolved ARPES.

Electron-phonon scattering contributes to superconductivity in the 2D states.

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.