Design of higher Chern number two-band structures from topological defect perspective.

In this article, we propose two methods for designing higher Chern number models from the topological defect perspective. Based on the fact that the Chern number is equal to a summation of the charges of meron defects, we show that the higher Chern number structures can be realized by either moving the positions of merons or increasing the amount of them. The combination of the two methods is also verified to be a viable approach. We shall construct several models and investigate their energy spectrum. More than one gapless state can be observed on the edges of these models. Expectedly, our theory promises to provide not only a simple approach to obtain the Chern number without computing any integrals, but also a practical technique for new material design.

Topological defects in Haldane model and higher Chern numbers in monolayer graphene.

We consider the Haldane model, a two-band model in monolayer graphene with non-trivial Chern numbers. Two types of topological defects, monopoles and merons, are derived from the model: (a) the monopole defects occur at the Dirac points, where the system experiences a topological transition and the Chern numberCtakes an indeterminate value. The sign-change of the mass term after this transition indicates different topological states labeled by differentCnumbers; (b) the meron defects occur as per a varying mass term. Summing up the topological charges of the merons leads to theCevaluation for the energy bands of an insulating bulk, and the result we obtain is in full agreement to the past literature. Furthermore, in this paper we propose a high-Cmodel through studying the limitation behavior of the Hamiltonian vector in the neighborhood of the topological defects. It is discovered that two conducting states may arise form the edges, where the lower band of the insulating bulk carries a higher Chern number,C=±2.

Heterovalent-Doping-Enabled Efficient Dopant Luminescence and Controllable Electronic Impurity Via a New Strategy of Preparing II-VI Nanocrystals.

Substitutional heterovalent doping represents an effective method to control the optical and electronic properties of nanocrystals (NCs). Highly monodisperse II-VI NCs with deep substitutional dopants are presented. The NCs exhibit stable, dominant, and strong dopant fluorescence, and control over n- and p-type electronic impurities is achieved. Large-scale, bottom-up superlattices of the NCs will speed up their application in electronic devices.