arXiv subjects

Yong-Cheng Jiang

Publications and source records attributed to Yong-Cheng Jiang.

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

Higher-order topology in honeycomb lattice with Y-Kekulé distortions

We investigate higher-order topological states in honeycomb lattice with Y-Kekulé distortions that preserve $C_{6v}$ crystalline symmetry. The gapped states in expanded and shrunken distortions are adiabatically connected to isolated hexamers and Y-shaped tetramer states, respectively, where the former possesses nontrivial higher-order topology characterized by a $\mathbb{Z}_6$ invariant. Topological corner states exist in a flake structure with expanded distortion where the hexamers are broken at the corners. Our work reveals that honeycomb lattice with Y-Kekulé distortions serves as a promising platform to study higher-order topological states.

cond-mat.mes-hall↗

arXiv2023

Possible gapless helical edge states in hydrogenated graphene

Electronic band structures in hydrogenated graphene are theoretically investigated by means of first-principle calculations and an effective tight-binding model. It is shown that regularly designed hydrogenation to graphene gives rise to a large band gap about 1 eV. Remarkably, by changing the spatial pattern of the hydrogenation, topologically distinct states can be realized, where the topological nontriviality is detected by $C_2$ parity indices in bulk and confirmed by the existence of gapless edge/interface states as protected by the mirror and sublattice symmetries. The analysis of the wave functions reveals that the helical edge states in hydrogenated graphene with the appropriate design carry pseudospin currents that are reminiscent of the quantum spin Hall effect. Our work shows the potential of hydrogenated graphene in pseudospin-based device applications.

cond-mat.mes-hall↗

arXiv2023

Topological electronic states in holey graphyne

We unveil that the holey graphyne (HGY), a two-dimensional carbon allotrope where benzene rings are connected by two $-$C$\equiv$C$-$ bonds fabricated recently in a bottom-up way, exhibits topological electronic states. Using first-principles calculations and Wannier tight-binding modeling, we discover a higher-order topological invariant associated with $C_2$ symmetry of the material, and show that the resultant corner modes appear in nanoflakes matching to the structure of precursor reported previously, which are ready for direct experimental observations. In addition, we find that a band inversion between emergent $g$-like and $h$-like orbitals gives rise to a nontrivial topology characterized by $\mathbb{Z}_2$ invariant protected by an energy gap as large as 0.52 eV, manifesting helical edge states mimicking those in the prominent quantum spin Hall effect, which can be accessed experimentally after hydrogenation in HGY. We hope these findings trigger interests towards exploring the topological electronic states in HGY and related future electronics applications.

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