Realizing a Superconducting Square-Lattice Bismuth Monolayer

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Low-dimensional materials with strong spin-orbit coupling (SOC) and crystal symmetry offer unique electronic and magnetic properties.
• Group 15 elements' 2D allotropes are promising due to tunable symmetries and topology under SOC.

Purpose of the Study:

• To heteroepitaxially grow a proximity-induced superconducting 2D square-lattice bismuth monolayer on superconducting lead (Pb) films.
• To investigate the structural, electronic, and potential topological properties of this novel material system.

Main Methods:

• Heteroepitaxial growth of 2D bismuth monolayer on superconducting Pb films.
• Scanning tunneling microscopy (STM) for structural resolution.
• Density functional theory (DFT) calculations for atomic and electronic structure analysis.

Main Results:

• Successfully grown square-lattice bismuth monolayer on Pb films with a stripey moiré structure, confirmed by STM.
• DFT calculations reveal a C₄ symmetry for the bismuth lattice.
• Predicted a Rashba-type spin-split Dirac band at the Fermi level, inducing superconductivity via proximity effect from the Pb substrate.

Conclusions:

• Introduced an intriguing material platform combining 2D Dirac bands, strong SOC, and superconductivity.
• Demonstrated proximity-induced superconductivity in a 2D bismuth monolayer.
• Suggested potential for topological superconducting states with magnetic doping or field application.