arXiv subjects

Xing-Xiang Wang

Publications and source records attributed to Xing-Xiang Wang.

5 recordsLinked to original sources

arXiv2026

Topological property of graphene with triangular array of nanoholes

The nontrivial band topology for graphene with regular arrays of nanoholes with $C_{6v}$ symmetry is investigated theoretically. For the case of $3\sqrt{3} \times 3\sqrt{3}$ triangular array of nanoholes, we find an energy gap at $Γ$ point around the Fermi level associated with a band inversion which induces change in parity indices, whereas deep below the Fermi level there are a bunch of valence bands characterized as obstructed atomic limit (OAL) which also accommodate imbalance in parity indices. This band structure renders the gap at the Fermi level topologically trivial and carrying no edge states, while the nontrivial band topology of the OAL manifests in two flat bands in the ribbon structure associated with localized electronic states at ribbon edges. The present results exhibit rich topological behaviors in graphene derivatives waiting for explorations.

cond-mat.mes-hall↗

arXiv2026

Periodic Behavior of Topology in Graphene with Nanohole Array

We derive a way to diagnose band topology for graphene with triangular and/or honeycomb array of nanoholes directly from the lattice constant of superstructure $m\sqrt{3}\times m\sqrt{3}$ with integer $m$. Taking into account the $C_{6v}$ crystalline symmetry respected by nanoholes and their array, we demonstrate that nontrivial topology appears periodically with $m$ with period two (six) for triangular (honeycomb) array. These behaviors are verified by Wyckoff positions of Wannier centers and parity index of valence bands at high-symmetry points in Brillouin zone. The results provide a convenient guide for material design of topological electronic states based on graphene derivatives.

cond-mat.mes-hall↗

arXiv2024

Comment on "Absence of Topological Protection of the Interface States in $\mathbb{Z}_2$ Photonic Crystals"

In the Letter, Xu et al. reported that edge modes disappear in the expanded structure of Wu-Hu model characterized by $\mathbb{Z}_2$ topological index, while appear in the trivial shrunken structure, when the edge cuts through the hexagonal unit cell. They then concluded that these edge modes are defect modes lacking topological protection. Unfortunately, their approach is not justified, rendering the conclusion unsolid.

physics.optics↗

arXiv2023

Interference and switching effect of topological interfacial modes with geometric phase

We investigate interference between topological interfacial modes in a semiconductor photonic crystal platform with Dirac frequency dispersions, which can be exploited for interferometry switch. It is showcased that, in a two-in/two-out structure with four topological waveguides, geometric phases of the two-component spinor wavefunctions of topological photonic modes accumulate at turning points of waveguides, which govern the interferences and split the electromagnetic energy into two output ports with relative power ratio tunable by the relative phase of inputs. We unveil that this brand-new photonic phenomenon is intimately related to the spin-momentum locking property of quantum spin Hall effect, and results from the symphonic contributions of three phase variables: the spinor phase and geometric phase upon design, and the global phase controlled from outside. The present findings open the door for manipulating topological interfacial modes, thus exposing a new facet of topological physics. The topology-driven interference can be incorporated into other devices which is expected to leave far-reaching impacts to advanced photonics, optomechanics and phononics applications.

physics.optics↗

arXiv2020

Comment on "Spin-Momentum-Locked Edge Mode for Topological Vortex Lasing, Phys. Rev. Lett. vol. 125, 013903 (2020)"

We present a comment on "Spin-Momentum-Locked Edge Mode for Topological Vortex Lasing, Phys. Rev. Lett. vol. 125, 013903 (2020)"(hereafter the Letter).In the Letter, Yang et al. reported on an elegant topological vortex laser and proposed that the near-field spin and OAM of the topological edge mode lasing have a one-to-one far-field radiation correspondence. The near-field information is based on frequency dispersions of the topological edge modes, without supporting measurements and/or computer simulations. Unfortunately, their frequency dispersions shown in Fig. 1(c) (see also Fig. S6 and Eqs. (5.3) and (5.4) in Supplemental Material) are wrong. As the result, the mode assignment of the main mode |-2,+> investigated in the Letter is mistaken, which should be |2,+>. This spoils the one-to-one correspondence claimed in the Letter.

physics.optics↗