No abstract

A model for the formation of helical multishell gold nanowires is proposed and is confirmed with quantum mechanical molecular dynamics simulations. The model can explain the magic number of the helical gold nanowires in the multishell structure. The reconstruction from ideal nonhelical to realistic helical nanowires consists of two stages: dissociations of atoms on the outermost shell from atoms on the inner shell and slip deformations of atom rows generating (111)-like structure on the outermost shell. The elementary processes are governed by competition between energy loss and gain by s and d electrons together with the width of the d band. The possibility for the helical nanowires of platinum, silver, and copper is discussed.

Relativistic spin-orbit interaction drastically modifies electronic band and endows emergent functionalities. One of the example is the Rashba effect 1,2 . In noncentrosymmetric systems such as interface 3 and polar materials 4,5 , the electronic band is spin-splitted depending on the momentum direction owing to the spin-orbit interaction, which is useful for the electric manipulation of spin current. Similar relativistic band-modification is also emergent for spin wave (magnon) in magnetic materials. The asymmetric magnon band dispersion induced by the Dzyaloshinskii-Moriya interaction 6,7 , which is antisymmetric exchange interaction originating from the spinorbit interaction, is theoretically expected 8,9 , and experimentally observed recently in noncentrosymmetric ferromagnets 10,11 . Here, we demonstrate that the nonreciprocal microwave response can be induced by the asymmetric magnon band in a noncentrosymmetric ferrimagnet LiFe 5 O 8 . This result may pave a new path to designing magnonic device based on the relativistic band engineering.

The 10-nm-scale structure in silicon cleavage is studied by the quantum mechanical calculations for large-scale electronic structure. The cleavage process on the order of 10 ps shows surface reconstruction and step formation. These processes are studied by analyzing electronic freedom and compared with STM experiments. The discussion presents the stability mechanism of the experimentally observed mode, the (111)-(2 × 1) mode, beyond the traditional approach with surface energy. Moreover, in several results, the cleavage path is bent into the experimentally observed planes, owing to the relative stability among different cleavage modes. Finally, several common aspects between cleavage and other phenomena are discussed from the viewpoints of the nonequilibrium process and the 10-nm-scale structure.