Rashba + exchange” effects in 1D magnets: bismuth nanoribbons as model systems

The Bi(111) bilayer is a 2D topological insulator and in the form of nanoribbons, it exhibits 1D spin-helical gapless edge states or quantum spin Hall effect (QSHE). In this QSHE phase, the system is non-magnetic. However, our first principles calculations show that Bi zigzag nanoribbons, like their graphene counterparts, can also exist in ferromagnetic and anti-ferromagnetic states, which are (meta)stable. These nanoribbons are useful model systems for studying “Rashba + exchange” effects in other possible 1D magnets. Although the magnetic Bi zigzag nanoribbons do not demonstrate QSHE, they still possess interesting physical properties associated with the interplay of Rashba and spin-orbit coupling. They exhibit a strong 1D Rashba effect, retain helical spin texture, become half-metallic with doping and, can have asymmetric transport properties.