title: Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling.
abstract: For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ≥ 0.5 eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states.
authors.affiliation: Department of Materials Science and Engineering, University of Utah, UT 84112.
authors.forename: Miao
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Department of Materials Science and Engineering, University of Utah, UT 84112.
authors.forename: Wenmei
authors.initials: W
authors.lastname: Ming
authors.affiliation: Department of Materials Science and Engineering, University of Utah, UT 84112.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, University of Utah, UT 84112.
authors.forename: Zhengfei
authors.initials: Z
authors.lastname: Wang
authors.affiliation: School of Physics, Beijing Institute of Technology, Beijing, China 100081.
authors.forename: Yugui
authors.initials: Y
authors.lastname: Yao
authors.affiliation: 1] Department of Materials Science and Engineering, University of Utah, UT 84112 [2] Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu