title: Two-Dimensional Large Gap Topological Insulators with Tunable Rashba Spin-Orbit Coupling in Group-IV films.
abstract: The coexistence of nontrivial topology and giant Rashba splitting, however, has rare been observed in two-dimensional (2D) films, limiting severely its potential applications at room temperature. Here, we through first-principles calculations to propose a series of inversion-asymmetric group-IV films, ABZ2(A ≠ B = Si, Ge, Sn, Pb; Z = F, Cl, Br), whose stability are confirmed by phonon spectrum calculations. The analyses of electronic structures reveal that they are intrinsic 2D TIs with a bulk gap as large as 0.74 eV, except for GeSiF2, SnSiCl2, GeSiCl2and GeSiBr2monolayers which can transform from normal to topological phases under appropriate tensile strain of 4, 4, 5, and 4%, respectively. The nontrivial topology is identified by Z2topological invariant together with helical edge states, as well as the berry curvature of these systems. Another prominent intriguing feature is the giant Rashba spin splitting with a magnitude reaching 0.15 eV, the largest value reported in 2D films so far. The tunability of Rashba SOC and band topology can be realized through achievable compressive/tensile strains (-4 ~ 6%). Also, the BaTe semiconductor is an ideal substrate for growing ABZ2films without destroying their nontrivial topology.
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Shou-Juan
authors.initials: SJ
authors.lastname: Zhang
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Wei-Xiao
authors.initials: WX
authors.lastname: Ji
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Chang-Wen
authors.initials: CW
authors.lastname: Zhang
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Pei-Ji
authors.initials: PJ
authors.lastname: Wang