Role of spin-orbit coupling for the band splitting in ⍺-Sb and ⍺-Bi on SiC(0001).

Monolayer atomic thin films of group-V elements have a high potential for application in spintronics and valleytronics because of their unique crystal structure and strong spin-orbit coupling. We fabricated Sb and Bi monolayers on a SiC(0001) substrate by the molecular-beam-epitaxy method and studied the electronic structure by angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations. The fabricated Sb film shows the (√3×√3)R30º superstructure associated with the formation of ⍺-Sb, and exhibits a semiconducting nature with a band gap of more than 1.8 eV. Spin-resolved ARPES measurements of isostructural ⍺-Bi revealed the in-plane spin polarization for the topmost valence band, demonstrating its Rashbasplittingof nature due to the space-inversion-symmetry breaking. We discuss the originobserved characteristic band structure and its similarity and difference between Sband Bi. .