Wide-range ideal 2D Rashba electron gas with large spin splitting in Bi_(2)Se_(3)/MoTe_(2) heterostructure

An application-expected ideal two-dimensional Rashba electron gas,i.e.,nearly all the conduction electrons occupy the Rashba bands,is crucial for semiconductor spintronic applications.We demonstrate that such an ideal two-dimensional Rashba electron gas with a large Rashba splitting can be realized in a topological insulator Bi_(2)Se_(3) ultrathin film grown on a transition metal dichalcogenides MoTe_(2) substrate through first-principle calculations.Our results show the Rashba bands exclusively over a very large energy interval of about 0.6 eV around the Fermi level within the MoTe2 semiconducting gap.Such a wide-range ideal twodimensional Rashba electron gas with a large spin splitting,which is desirable for real devices utilizing the Rashba effect,has never been found before.Due to the strong spin-orbit coupling,the strength of the Rashba splitting is comparable with that of the heavy-metal surfaces such as Au and Bi surfaces,giving rise to a spin precession length as small as~10 nm.The maximum in-plane spin polarization of the inner(outer)Rashba band near theΓpoint is about 70%(60%).The room-temperature coherence length is at least several times longer than the spin precession length,providing good coherency through the spin processing devices.The wide energy window for ideal Rashba bands,small spin precession length,as well as long spin coherence length in this twodimensional topological insulator/transition metal dichalcogenides heterostructure pave the way for realizing an ultrathin nanoscale spintronic device such as the Datta-Das spin transistor at room-temperature.