Giant tunable Rashba spin splitting in two-dimensional BiSb monolayer and BiSb/AlN heterostructures

摘要

Search of novel two-dimensional giant Rashba semiconductors is a crucial stepin the development of the forthcoming nano-spintronics technology. Usingfirst-principle calculations, we study a stable two-dimensional crystal phaseof BiSb having buckled honeycomb lattice geometry, which is yet unexplored. Thephonon, room temperature molecular dynamics and elastic constant calculationsverify the dynamical and mechanical stability of the monolayer at 0~K and atroom temperature. The calculated electronic bandstructure reveals the directbandgap semiconducting nature of BiSb monolayer with presence of highly mobiletwo-dimensional electron gas (2DEG) near Fermi-level. Inclusion of spin-orbitcoupling (SOC) yields the giant Rashba spin-splitting of 2DEG near Fermi-level.The calculated Rashba energy and Rashba splitting constant are 13 meV and 2.3eV\AA, respectively. The strength of the Rashba splitting is amongst thelargest yet known 2D Rashba semiconductors. We demonstrate that the strength ofthe Rashba spin-splitting can be significantly tuned by applying in-planebi-axial strain on the BiSb monolayer. Presence of the giant Rashbaspin-splitting together with the large electronic bandgap (1.6 eV) makes thissystem of peculiar interest for optoelectronics applications. Furthermore, westudy the electronic properties of BiSb/AlN heterostructures having a latticemismatch of 1.3\% at the interface. Our results suggest that BiSb monolayer andheterostructure systems could be potentially used to develop highly efficientspin field-effect transistors, optoelectronics and nano-spintronics devices.Thus, this comprehensive study of two-dimensional BiSb systems can expand therange of possible applications in the future spintronics technology.