arXiv subjects

Cheng-Hsueh Yang

Publications and source records attributed to Cheng-Hsueh Yang.

3 recordsLinked to original sources

arXiv2023

Fractal-like star-mesh transformations using graphene quantum Hall arrays

A mathematical approach is adopted for optimizing the number of total device elements required for obtaining high effective quantized resistances in graphene-based quantum Hall array devices. This work explores an analytical extension to the use of star-mesh transformations such that fractal-like, or recursive, device designs can yield high enough resistances (like 1 EΩ, arguably the highest resistance with meaningful applicability) while still being feasible to build with modern fabrication techniques. Epitaxial graphene elements are tested, whose quantized Hall resistance at the nu=2 plateau (R_H = 12906.4 Ω) becomes the building block for larger effective, quantized resistances. It is demonstrated that, mathematically, one would not need more than 200 elements to achieve the highest pertinent resistances

cond-mat.mes-hall↗

arXiv2021

Temperature-induced Coulomb excitations in rhombohedral 3D graphene

Low-energy electronic properties of ABC-stacked graphite are studied by the tight-binding model. There are linear and parabolic bands with and without degeneracy. They show strongly anisotropic dispersions. ABC-stacked grahite is a semimetal due to slight overlapping near the Fermi level beween conduction and valence bands. The interlayer interactions could change the energy dispersion, state degeneracy, and positions of band-crossing and band-edge state. Density of states exhibit a shoulder structure, owing to band-edge states near or at high symmetric points. Low-frequency Coulomb excitation properties with different transferred momenta (${\bf q}'$s) are further studied within the random phase approximation. The Landau dampings is too serious under the parallel transferred momentum (${\bf q}\perp \hat z$); therefore, it is impossible to observe the 3D optical plasmons. However, even for the perpendicular transferred momentum (${\bf q}\parallel \hat z$), the full assistance due to the thermal excitations is necessary to induce the collective charge oscillations along the $z$-axis. The height and position of temperature-induced plasmon peak in the energy loss spectrum are greatly enhanced by the increasing temperature, but weakly depend on the various transferred momenta. These features are very different from AA- and AB-stacked graphites.

cond-mat.mtrl-sci↗

arXiv2020

Dimension-and lattice-diversified Coulomb excitations in3D,2D,1D-nanotube electron gases,graphene and carbon nanotube

Elementary electronic excitations, which are due to the Coulomb-field scatterings, present the diverse phenomena in 3D, 2D, 1D-nanotube electron gases, graphene and carbon nanotubes. The critical mechanisms cover the dimension-dependent bare Coulomb potentials, energy dispersions, and free/valence carrier density. They are responsible for the main features, the available excitation channels (the electron-hole regions), the joint van Hove singularities, the undamped/damped collective excitations at small/sufficiently high transferred momenta, the momentum dependences of plasmon frequencies (acoustic and optical modes), and their categories (the intraband and inter-pi-band plasmons). There exists certain significant similarities and difference among various systems. The (momentum/ angular momentum, frequency)-excitation phase diagrams are directly reflected in the propagation of plasma waves.

cond-mat.mes-hall↗