Photonic half-semimetals with dual semimetal-insulator topology
Abstract
Topological wave systems have largely evolved along two distinct paradigms: gapless topological semimetals and gapped topological insulators. While topological semimetals support bulk transport, they generally lack intrinsic selectivity among propagation channels; topological insulators enable robust transport but confine it to narrow interfaces, limiting spatial utilization. Here, we theoretically demonstrate and experimentally realize time-reversal-invariant spin-valley photonic half-semimetals (HSMs), which exhibit a dual semimetal-insulator topology within a single bulk band structure. In HSMs, the bandgap closes selectively in spin-valley space: for a given spin (valley), one valley (spin) is semimetallic while the other remains insulating. This coexistence of spin- and valley-resolved gapless and gapped band structures makes HSMs fundamentally distinct from both conventional semimetals and insulators. As a defining bulk phenomenon, an HSM functions as a spin-valley-locked beam splitter, intrinsically enabling valley-selective spin routing. Moreover, when four complementary HSMs are assembled into a periodic superlattice, the same dual topology enables reciprocal spin-valley-resolved multilane helical transport with 100% spatial utilization. These results establish HSMs as a platform for selective bulk wave control and multichannel topological transport beyond conventional topological phases.
Related
- Plasmon modes in three-dimensional multifold semimetals. I. Triple-point semimetal, its quadratic cousin, and Hopf semimetal
- Triple-band nonreciprocal optical Tamm states in a Weyl-semimetal/Fibonacci-type photonic heterostructure
- Helical Anomaly from Concurrent ℤ and ℤ2 Topology in an Acoustic Semimetal
- High-Throughput Discovery of Chiral Carbon-Boron Semimetals with Weyl Topology and Phonon-Mediated Superconductivity
- Robust multichannel bulk transport in a time-reversal-invariant insulator-free photonic waveguide array
BibTeX
@misc{gao2026photonic,
title = {{Photonic half-semimetals with dual semimetal-insulator topology}},
author = {Zi-Xuan Gao and Xiaohan Cui and Xiao-Dong Chen and Ke-Yi Zeng and Hao-Chang Mo and Xin-Tao He and Ruo-Yang Zhang and C. T. Chan and Jian-Wen Dong},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25596},
eprint = {2609.25596},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25596},
}
RIS
TY - UNPB
TI - Photonic half-semimetals with dual semimetal-insulator topology
AU - Zi-Xuan Gao
AU - Xiaohan Cui
AU - Xiao-Dong Chen
AU - Ke-Yi Zeng
AU - Hao-Chang Mo
AU - Xin-Tao He
AU - Ruo-Yang Zhang
AU - C. T. Chan
AU - Jian-Wen Dong
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.25596
UR - https://arxiv.org/abs/2609.25596
AB - Topological wave systems have largely evolved along two distinct paradigms: gapless topological semimetals and gapped topological insulators. While topological semimetals support bulk transport, they generally lack intrinsic selectivity among propagation channels; topological insulators enable robust transport but confine it to narrow interfaces, limiting spatial utilization. Here, we theoretically demonstrate and experimentally realize time-reversal-invariant spin-valley photonic half-semimetals (HSMs), which exhibit a dual semimetal-insulator topology within a single bulk band structure. In HSMs, the bandgap closes selectively in spin-valley space: for a given spin (valley), one valley (spin) is semimetallic while the other remains insulating. This coexistence of spin- and valley-resolved gapless and gapped band structures makes HSMs fundamentally distinct from both conventional semimetals and insulators. As a defining bulk phenomenon, an HSM functions as a spin-valley-locked beam splitter, intrinsically enabling valley-selective spin routing. Moreover, when four complementary HSMs are assembled into a periodic superlattice, the same dual topology enables reciprocal spin-valley-resolved multilane helical transport with 100% spatial utilization. These results establish HSMs as a platform for selective bulk wave control and multichannel topological transport beyond conventional topological phases.
ER -