Tunable topological quantum states in three- and two-dimensional materials

Abstract

We review our theoretical advances in tunable topological quantum states in three-and twodimensional materials with strong spin-orbital couplings. In three-dimensional systems, we propose a new tunable topological insulator, bismuth-based skutterudites in which topological insulating states can be induced by external strains. The orbitals involved in the topological band-inversion process are the d-and p-orbitals, unlike typical topological insulators such as Bi 2 Se 3 and BiTeI, where only the p-orbitals are involved in the band-inversion process. Owing to the presence of large d-electronic states, the electronic interaction in our proposed topological insulator is much stronger than that in other conventional topological insulators. In two-dimensional systems, we investigated 3d-transition-metal-doped silicene. Using both an analytical model and first-principles Wannier interpolation, we demonstrate that silicene decorated with certain 3d transition metals such as vanadium can sustain a stable quantum anomalous Hall effect. We also predict that the quantum valley Hall effect and electrically tunable topological states could be realized in certain transition-metal-doped silicenes where the energy band inversion occurs. These findings provide realistic materials in which topological states could be arbitrarily controlled.

Aluminum functionalized few-layer silicene as anode material for alkali metal ion batteries

“…Silicene is made of silicon, one of the most abundant chemical elements on Earth, which is also environmentally friendly and compatible with the current silicon-based microelectronics devices. 11,12 Furthermore, it has been determined theoretically that the single-layer silicene has a 954 mAh g −1 capacity for LIBs and SIBs, 13,14 larger than that of graphite.…”

Electronic, mechanical, optical and photocatalytic properties of two-dimensional Janus XGaInY (X, Y ;= S, Se and Te) monolayers

“…1) opened up a new pathway for materials scientists to search for new graphene-like 2D materials. Due to extensive studies on graphene, 2D layered materials, including MXenes, 2 phosphorene, 3 analogous binary materials, 4 transition metal dichalcogenides (TMDCs), 5,6 Janus TMDCs, 7,8 silicene, [9][10][11] etc., have been theoretically predicted and experimentally synthesized for various interesting applications in photocatalysis and optoelectronic devices. 12,13 Among them, the semiconductor group-III monochalcogenides have been comprehensively studied for their prospective applications in the eld, such as in the conversion of solar energy.…”

Complex energy plane and topological invariant in non-Hermitian systems

“…The non-Hermitian systems contain complex eigen energies and nonorthogonal eigenstates, which motivate many attempts to explore their novel physical phenomena and potential applications beyond conventional Hermitian systems, and to explore what novel mathematical structures exist beyond those of canonical quantum mechanics [3,8,9]. A lot of efforts have been focused on the classification of the topological equivalence classes based on the symmetry of systems in condensed matter physics and on the physical properties of these topological phases, as well as their potential applications [2,3,[10][11][12][13][14][15].…”