Towards topological quasifreestanding stanene via substrate engineering

Abstract

In search for a new generation of spintronics hardware, material candidates for room temperature quantum spin Hall effect (QSHE) have become a contemporary focus of investigation. Inspired by the original proposal for QSHE in graphene, several heterostructures have been synthesized, aiming at a hexagonal monolayer of heavier group IV elements promoting the QSHE bulk gap via increased spin-orbit coupling. So far, the monolayer/substrate coupling, which can manifest itself in strain, deformation, and hybridization, has proven to be detrimental to the aspired QSHE conditions for the monolayer. For stanene, the Sn analogue of graphene, we investigate how an interposing buffer layer mediates between monolayer and substrate in order to optimize the QSHE setting. From a detailed density functional theory study, we highlight the principal mechanisms induced by such a buffer layer to accomplish quasi-freestanding stanene in its QSHE phase. We complement our theoretical predictions by presenting the first attempts to grow a buffer layer on SiC (0001) on which stanene can be deposited. arXiv:1807.09006v2 [cond-mat.mtrl-sci] 6 Nov 2018 E = 40 eV Caption of figure: LEED image of Al-( 3× 3)R30°on Si-terminated 4H-SiC(0001) recorded with an electron energy of 40 eV. The dashed hexagonal Brillouin zones in red and blue highlight the Al induced ( 3× 3) and (1×1) spots, respectively.

Atomically Thin Quantum Spin Hall Insulators

“…[85] While the intrinsic band structures of all higher-Z Xenes are predicted to be similar to that of graphene, [85,90,106,[112][113][114][115] the increased orbital overlap due to buckling contributes to a slight increase in the SO gap. [85] As a consequence of their orbital structure, QSH behavior in Xenes may be tuned by orbital hybridization (for example, via substrate interactions [116,117] ), or induced by lattice strain, [105] as well as by chemical functionalization with impurities or functional groups. [90,118] In buckled stanene, for example, compressive strain leads to an increase of the p x,y + orbital energy above the Fermi level at Γ, rendering the material metallic.…”

Heterostructures of Graphene and Topological Insulators Bi2Se3, Bi2Te3, and Sb2Te3

“…To understand the proximity effect on the electronic band structure of graphene, we first introduce a generic phenomenological model describing Dirac states of graphene with reduced symmetry due to external effects. [ 17,18,20,62,63,64,65,66 ] The model Hamiltonian given in the basis , , , and reads…”

Xenes as an Emerging 2D Monoelemental Family: Fundamental Electrochemistry and Energy Applications

“…Through the above analysis, the main reasons for the attractive application prospect of Xenes in the field of electrochemistry are summarized as follows: 1) a large surface-active site density can be contributed by high surface to bulk ratios for impressive applications in the surface-involving reactions, [148] and electrode-electrolyte accessibilities can also be promoted with remarkably highmaterial utilization; [149][150][151] 2) Xenes endows a successive and shortening ion/electron channel, which can improve ion/electron conductivities [152][153][154] and secure fast reaction kinetics; [142,155] 3) the increased interlayer spacing provides enough large interspaces to buffer the volumetric expansion during electrochemical reactions; 4) considering alloying reaction mechanism of group IV and group V Xenes, they must own ultrahigh specific capacities for alkaline ion batteries; [102,153,[156][157][158] 5) Xenes with strong flexibility can self-relieve the volume expansion and structural deformation at a large degree during the electrochemical reactions; [54,159] 6) Xenes with excellent mechanical properties as protective films to cover the current collector, have enough high strength to restrain growth of metal dendrites; 7) the physicochemical properties of Xenes are easily adjusted due to the surface exposed lone pair electrons, which give them with vivid electrochemical reactivities and flexibilities of various chemical functionalities; 8) Xenes as block unites can be used to construct various fantastic micro-/ nano-structures [115,[160][161][162] for various amazing applications; 9) relatively simple atomic arrangement, which enables easy investigation and modeling for exploring the novel mechanism in the related application. [26,163] In summary, Xenes are considered to be the star material in future electrochemical applications with high capacity, high speed, high safety, and flexibility due to its unique structure, electronic and other characteristics.…”