The three-dimensional ternary LiFeO2 compound presents various unusual essential properties. The main features are thoroughly explored by the density functional and many-body perturbation theory. The concise physical/chemical picture, the critical sp
in-polarizations and orbital hybridizations in the Li-O and Fe-O bonds, are clearly examined through geometric optimization, quasi-particle energy spectra, spin-polarized density of states, the spatial charge densities, the spin-density distributions, and the strong optical responses. The unusual optical transitions cover various frequency-dependent absorption structures, and the most prominent plasmon modes are identified by the dielectric functions, energy loss functions, reflectance spectra, and absorption coefficients. Optical excitations are anisotropic and strongly affected by excitonic effects. The close combinations of electronic, magnetic and optical properties allow us to identify the significant spin-polarizations and orbital hybridizations for each available excitation channel. The lithium ferrite compound can be used for spintronic and photo-catalysis applications.
The Li2SiO3 compound, a ternary electrolyte compound of Lithium-ion based batteries, exhibits unique geometric and band structures, an atom-dominated energy spectrum, charge densities distributions, atom and orbital-projected density of states, and s
trong optical responses. The state-of-the-art analysis, based on an ab-initio simulation, have successfully confirmed the concise physical/chemical picture and the orbital bonding in Li-O and Si-O bonds. Additionally, the unusual optical response behavior includes a large redshift of the onset frequency due to the extremely strong excitonic effect, the polarization of optical properties along three-directions, 22 optical excitations structures and the most prominent plasmon mode in terms of the dielectric functions, energy loss functions, absorption coefficients, and reflectance spectra. The close connections of electronic and optical properties can identify a specific orbital hybridization for each distinct excitation channel. The developed theoretical framework will be very appropriate for fully comprehending the diverse phenomena of cathode/electrolyte/anode materials in ion-based batteries.
The generalized tight-binding model is developed to investigate the magneto-electronic properties in twisted bilayer graphene system. All the interlayer and intralayer atomic interactions are included in the Moire superlattice. The twisted bilayer gr
aphene system is a zero-gap semiconductor with double-degenerate Dirac-cone structures, and saddle-point energy dispersions appearing at low energies for cases of small twisting angles. There exist rich and unique magnetic quantization phenomena, in which many Landau-level subgroups are induced due to specific Moire zone folding through modulating the various stacking angles. The Landau-level spectrum shows hybridized characteristics associated with the those in monolayer, and AA $&$ AB stackings. The complex relations among the different sublattices on the same and different graphene layers are explored in detail.
The electronic properties and optical excitations are investigated in the geometry- and field-modulated bilayer graphene systems, respectively, by using the tight-binding model and Kubo formula. The stacking symmetry of bilayer graphene can be manipu
lated by varying the width and position of domain wall (DW) within two normally stacked graphene. All the layer-dependent atomic interactions are taken into consideration under external fields. The modulation of stacking configuration gives rise to significant effects of zone folding on energy subbands, subenvelope wave functions, density of states, and optical absorption spectra. This study clearly illustrates the diverse 1D phenomena in the energy band structure and absorption spectra; the DW- and $V_z$-created dramatic variations are comprehensively explored under accurate calculations and delicate analysis. Concise physical pictures are proposed to give further insight into the quasi-1D behaviors.
The layer-based random-phase approximation is further developed to investigate electronic excitations in tri-layer ABC-stacked graphene. All the layer-dependent atomic interactions and Coulomb interactions are included in the dynamic charge screening
. There exist rich and unique (momentum, frequency)-excitation phase diagrams, in which the complex single-particle excitations and five kinds of plasmon modes, are dominated by the unusual energy bands and doping carrier densities. The latter frequently experience the significant Landau damping due to the former, leading to the coexistence/destruction in the energy loss spectra. Specifically, the dispersion of the only acoustic plasmon in pristine case is dramatically changed from linear into quadratic even at very low doping.
The magneto-optical properties of simple hexagonal graphite exhibit rich beating oscillations, which are dominated by the field strength and photon energy. The former has a strong effect on the intensity, the energy range of the beating and the numbe
r of groups, and the latter modulates the total group numbers of the oscillation structures. The single-particle and collective excitations are simultaneously presented in the magnetoreflectance spectra and can be precisely distinguished. For the loss function and reflectance, the beating pattern of the first group displays stronger intensities and broader energy range than other groups. Simple hexagonal graphite possesses unique magneto-optical characteristics that can serve to identify other bulk graphites.
We use a tight-binding model and the random-phase approximation to study the Coulomb excitations in simple-hexagonal-stacking multilayer graphene and discuss the field effects. The calculation results include the energy bands, the response functions,
and the plasmon dispersions. A perpendicular electric field is predicted to induce significant charge transfer and thus capable of manipulating the energy, intensity, and the number of plasmon modes. This could be further validated by inelastic light scattering or electron-energy-loss spectroscopy.
