Giant Rashba splitting in a 2D BiAs layer on InAs(111)B

Bismuth-based compounds, such as Bi1 -x Sb x or Bi 2 Te 3 , have outstanding electronic properties especially for advanced quantum devices. However, the potential of low-dimensional group V-Bi materials is largely undetermined. Here, we report the experimental realization of a two-dimensional (2D) BiAs layer with giant Rashba spin splitting, grown on an InAs(111)B substrate via molecular beam epitaxy. ARPES reveals the emergence of a prominent M-shaped band structure and a distinct electron pocket at the Fermi level. DFT, complemented by synchrotron-based XPS, LEED, and STM, confirms strong spin-orbit coupling and a giant Rashba coefficient of these electronic states. An As overlayer, remaining from the fabrication process, preserves a structural shift between substrate and BiAs layer, essential for the Rashba splitting, while preventing undesirable reconstruction. This indicates how well-known capping techniques can stabilize new 2D compounds with interesting electronic structures, especially BiAs, a promising candidate to open possibilities for next-generation spintronic devices and field-effect transistors.