Two-Dimensional Superconductor with a Giant Rashba Effect: One-Atom-Layer Tl-Pb Compound on Si(111)

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• The search for novel two-dimensional (2D) materials with unique electronic properties is a key area in condensed matter physics.
• Rashba-type spin splitting in metallic surface states is crucial for spintronic applications.
• Understanding superconductivity in low-dimensional systems is vital for next-generation electronic devices.

Purpose of the Study:

• To investigate the electronic and superconducting properties of a one-atom-layer Tl-Pb compound on a Si(111) surface.
• To explore the phenomenon of giant Rashba-type spin splitting in this novel 2D system.
• To elucidate the mechanism of superconductivity and electron-phonon coupling.

Main Methods:

• Fabrication of a one-atom-layer Tl-Pb compound on Si(111) with √3×√3 periodicity.
• Temperature-dependent angle-resolved photoelectron spectroscopy (ARPES) to study band structure and electron-phonon coupling.
• In situ micro-four-point-probe conductivity measurements under magnetic field to determine superconducting transition temperature and mechanism.

Main Results:

• The (Tl, Pb)/Si(111) system demonstrated a giant Rashba-type spin splitting of metallic surface-state bands.
• Two-dimensional superconducting transport properties were observed, with the superconducting state emerging at 2.25 K.
• Enhanced electron-phonon coupling was detected for one of the spin-split bands, consistent with the Berezinskii-Kosterlitz-Thouless mechanism.

Conclusions:

• The 2D Tl-Pb compound on Si(111) is a prototypical system for studying the interplay of spin splitting and superconductivity.
• This material offers a unique platform for investigating superconducting 2D systems with lifted spin degeneracy.
• The well-established composition, atomic structure, and electronic band structure facilitate further research into its intriguing properties.