Electronic structure and relaxation dynamics in a superconducting topological material.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Topological superconductors exhibit unique quantum states, including gapless surface states crucial for realizing Majorana fermions.
• Strontium-intercalated Bismuth Selenide (SrₓBi₂Se₃) has emerged as a promising topological superconductor with a critical temperature (Tc) around 3 K.

Purpose of the Study:

• To investigate the normal state electronic structure and surface states of SrₓBi₂Se₃.
• To understand the relaxation dynamics of different electronic states and their relation to superconductivity.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) to probe electronic structure.
• Time-resolved ARPES to study carrier dynamics.
• First-principles calculations to support experimental findings.

Main Results:

• Observation of a quantum well confined two-dimensional (2D) state alongside a topological surface state in Sr₀.₀₆Bi₂Se₃ (Tc ≈ 2.5 K).
• Distinct relaxation dynamics observed between the topological surface states and the 2D states.
• Experimental data explained by intra-band scattering for topological surface states and electron-phonon scattering for 2D states, linking 2D states to superconductivity.

Conclusions:

• The coexistence of distinct electronic states in SrₓBi₂Se₃ provides insights into its topological superconducting properties.
• Electron-phonon scattering in the 2D states is identified as a crucial mechanism for superconductivity in this material.
• These findings contribute to the understanding of low-temperature superconductivity in topological materials.