title: Epitaxial growth of large-gap quantum spin Hall insulator on semiconductor surface.
abstract: Formation of topological quantum phase on a conventional semiconductor surface is of both scientific and technological interest. Here, we demonstrate epitaxial growth of 2D topological insulator, i.e., quantum spin Hall state, on Si(111) surface with a large energy gap, based on first-principles calculations. We show that the Si(111) surface functionalized with one-third monolayer of halogen atoms [Si(111)-√3 x √3 -X (X = Cl, Br, I)] exhibiting a trigonal superstructure provides an ideal template for epitaxial growth of heavy metals, such as Bi, which self-assemble into a hexagonal lattice with high kinetic and thermodynamic stability. Most remarkably, the Bi overlayer is atomically bonded to but electronically decoupled from the underlying Si substrate, exhibiting isolated quantum spin Hall state with an energy gap as large as ∼ 0.8 eV. This surprising phenomenon originates from an intriguing substrate-orbital-filtering effect, which critically selects the orbital composition around the Fermi level, leading to different topological phases. In particular, the substrate-orbital-filtering effect converts the otherwise topologically trivial freestanding Bi lattice into a nontrivial phase; and the reverse is true for Au lattice. The underlying physical mechanism is generally applicable, opening a new and exciting avenue for exploration of large-gap topological surface/interface states.
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112;
authors.forename: Miao
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112;
authors.forename: Wenmei
authors.initials: W
authors.lastname: Ming
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112;
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112;
authors.forename: Zhengfei
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112; School of Physics and Technology, University of Jinan, Jinan, Shangdong 250022, China; and.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112; Collaborative Innovation Center of Quantum Matter, Beijing 100871, China fliu@eng.utah.edu.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu