arXiv subjects

Phusit Nualpijit

Publications and source records attributed to Phusit Nualpijit.

5 recordsLinked to original sources

arXiv2025

Strain-Tuned Optical Properties of a Two-Dimensional Hexagonal Lattice: Exploiting Saddle Degrees of Freedom and Saddle Filtering Effects

The deformation of hexagonal lattices has attracted considerable attention due to its promising applications in straintronics. This study employs the tight-binding model to investigate the anisotropic spectrum, where electronic transport can be manipulated by the degree of deformation. The longitudinal conductivities, light transmittance, and absorbance are analyzed, revealing enhancement along one direction and suppression along the other. The findings indicate that the direction and magnitude of strain can be determined by measuring transmittance and absorbance, showing significant deviations from the unstrained condition. Furthermore, a strong absorbance is observed due to the interband transition of electrons near the M-point saddles, linked to van Hove singularities for specific values of nearest and next-nearest hoping energy. The unexpected characteristics of saddle polarization-analogous to valley polarization at K- and K'-become particularly prominent when strain affects the selection of M-point saddle. Notably, the demonstration indicates that a highly efficient M-point saddle filtering effect takes place, induced by linearly polarized light. This model paves the way for exploring the optical properties of anisotropic hexagonal lattices, such as black phosphorus and borophene oxide. These results also open a pathway to strain-programmable optoelectronic devices, such as polarization-selective photodetectors, tunable absorbers, and ultrathin optical filters.

cond-mat.mes-hall↗

arXiv2024

Triplet fermions in MXenes: The Applications for spintronic-based devices

We investigate the electronic properties of MXenes by three bands tight-binding model of \d_{z^2} , \d_{xy} , and \d_{x^2-y^2} orbitals. The three corresponding bands touch each other at high symmetry K point in the case of absence of spin-orbit interaction. The proper parameters can be obtained by Slater-Koster parameters related to chemical bonding, π, σ, and δbonds. The model calculated for these band structures make an agreement with the same trend as discussed in DFT calculation which the hopping parameters may be identified roughly by fermi velocity. Furthermore, the triplet fermion occurs around K point hosting by flat band, leading to super-Klein tunnelling and anti-super-Klein tunnelling for gapped and gapless pseudospin-1 fermion, respectively. These may apply for nanodevices operated by spin polarization which is more stable than that of the conventional two-dimensional materials.

cond-mat.mtrl-sci↗

arXiv2023

Spin-valley Hall effects and pseudospin-1 system in transition-metal dichalcogenides: three band model approach

The energy spectra of transition metal dichalcogenides are primarily influenced by the and orbitals. This results in a three-band model characterized by strong spin-orbit interaction. Investigating these bands using a projection into a two-band model is adequate for exploring electronic and optical properties. The topological phases, spin-valley Hall effect, derived from spin-valley Chern numbers, are also examined. The inclusion of spin-orbit interaction breaks inversion symmetry while maintaining time-reversal symmetry. This leads to the non-zero spin-valley dependent Hall conductivities, pivotal for both the spin Hall and valley Hall effects. These phenomena could have applications beyond traditional electronics, potentially encoding quantum bits. In particular, electrons at high-symmetry points, namely the K and K' points, might behave as if they are in a pseudospin-1 system with spin angular momentum of and , leading to triplet energy states. Such predictions could encourage super-Klein tunneling, which might offer insights into Majorana fermions, relevant for topological quantum computation.

cond-mat.mes-hall↗

arXiv2023

Control of valley optical conductivity and topological phases in buckled hexagonal lattice by orientation of in-plane magnetic field

We investigate the optical conductivity, along with longitudinal and transverse conductivities, in buckled hexagonal lattice such as silicene subjected to both an in-plane magnetic field and a perpendicular electric field. In this model, we neglect the effect of the spin-orbit interaction, which is of a smaller order compared to the strong staggered potential and the next-nearest hoping energy. The orientations of the in-plane magnetic field and the perpendicular electric field give rise to a non-uniform, tunable gap. The Chern number for each valley degree of freedom deviates from being constant but remains steady when summed over the entire Brillouin zone. The longitudinal and transverse currents, in the case of a specific valley, can be selected by adjusting the direction of the electric field in the semimetal phase. Furthermore, the defining characteristics of topological phases induces the rapid change in longitudinal conductivity when varying the angle of orientation of the in-plane magnetic field under monochromatic light, and perfect valley filtering in transverse conductivity. The transverse current associated with a specific valley can be selected when the angle of orientation satisfies the specific conditions. This investigation paves the way for materials design with valley-locked current, using a specific orientation of the in-plane magnetic field.

cond-mat.mes-hall↗

arXiv2018

Tunable transmittance in anisotropic 2D materials

A uniaxial strain applied to graphene-like materials moves the Dirac nodes along the boundary of the Brillouin zone. An extreme case is the merging of the Dirac node positions to a single degenerate spectral node which gives rise to a new topological phase. Then isotropic Dirac nodes are replaced by a node with a linear behavior in one and a parabolic behavior in the other direction. This anisotropy influences substantially the optical properties. We propose a method to determine characteristic spectral and transport properties in black phosphorus layers which were recently studied by several groups with angle-resolved photoemission spectroscopy, and discuss how the transmittance, the reflectance and the optical absorption of this material can be tuned. In particular, we demonstrate that the transmittance of linearly polarized incident light varies from nearly 0\% to almost 100\% in the microwave and far-infrared regime.

cond-mat.mes-hall↗