arXiv subjects

Ching-Hong Ho

Publications and source records attributed to Ching-Hong Ho.

4 recordsLinked to original sources

arXiv2019

Diverse quantization phenomena in layered materials

The diverse quantization phenomena in 2D condensed-matter systems, being due to a uniform perpendicular magnetic field and the geometry-created lattice symmetries, are the focuses of this book. They cover the diversified magneto-electronic properties, the various magneto-optical selection rules, the unusual quantum Hall conductivities, and the single- and many-particle magneto-Coulomb excitations. The rich and unique behaviors are clearly revealed in few-layer graphene systems with the distinct stacking configurations, the stacking-modulated structures, and the silicon-doped lattices, bilayer silicene/germanene systems with the bottom-top and bottom-bottom buckling structures, monolayer and bilayer phosphorene systems, and quantum topological insulators. The generalized tight-binding model, the static and dynamic Kubo formulas, and the random-phase approximation, are developed/modified to thoroughly explore the fundamental properties and propose the concise physical pictures. The different high-resolution experimental measurements are discussed in detail, and they are consistent with the theoretical predictions.

physics.comp-ph↗

arXiv2017

Chiral symmetry classes and Dirac nodal lines in three-dimensional layered systems

We study the existence and stability of Dirac nodal lines in three-dimensional layered systems, whose layers individually have Dirac nodal points protected by chiral (sublattice) symmetry. The model system we consider is the rhombohedral stack of graphene layers with each layer subjected to a uniform external potential that respects either AIII or BDI classes. From the Hamiltonians in either classes, a pair of nontrivial spiraling Dirac nodal lines can be derived. The results are reasonable in accord to the topological classification of gapless phases for codimension $2$. The nodal lines approach each other as the magnitude of the potential increases, revealing their annihilation due to the fact that regarding the full system their topological invariants are cancelled out.

cond-mat.mes-hall↗

arXiv2015

Magnetoelectronic and optical properties of nonuniform graphene nanoribbons

The electronic and optical properties of nonuniform bilayer graphene nanoribbons are worth investigating as they exhibit rich magnetic quantization. Based on our numerical results, their electronic and optical properties strongly depend on the competition between magnetic quantization, lateral confinement, and stacking configuration. The results of our calculations lead to four categories of magneto-electronic energy spectra, namely monolayer-like, bilayer-like, coexistent, and irregular quasi-Landau-level like. Various types of spectra described in this paper are mainly characterized by unusual spatial distributions of wave functions in the system under study. In our paper, we demonstrate that these unusual quantized modes lead to the appearance of such diverse magneto-optical spectra. Moreover, the investigation of the density of states in our model leads to the appearance of many prominent symmetric and weakly asymmetric peaks. The almost well-behaved quasi-Landau levels exhibit high-intensity peaks with specific selection rules, and the distorted energy subbands present numerous low-intensity peaks without any selection rules.

physics.comp-ph↗

arXiv2015

Evolution and dimensional crossover from the bulk subbands in ABC-stacked graphene to a three-dimensional Dirac cone structure in rhombohedral graphite

The band structure of ABC-stacked N-layer graphene comprises topologically corresponding flat surface and gapped bulk subbands, as a consequence of the unique stacking configuration. In this paper, the bulk subbands are for the first times ever obtained for arbitrary N. A non-perturbative effective Hamiltonian closed in the bulk subspace is derived and used. The gapped bulk subbands are shown to evolve towards the zero energy with increasing N and in the infinite limit, they touch linearly along a circle. This outcome is a manifestation of the dimensional crossover to a three-dimensional Dirac cone structure known to exist in the bulk of rhombohedral graphite. The Dirac points, forming continuous nodal lines in a spiraling fashion, are projected onto the circle, within which the surface subbands are confined and flatten.

cond-mat.mes-hall↗