# Symmetry-enforced band topology observed in TiAs single crystals

> Researchers grew stoichiometric hexagonal TiAs single crystals by chemical vapour transport and combined spectroscopy, ARPES, transport measurements and calculations. Four Raman-active vibrational modes were observed, while calculations indicated symmetry-protected topological band crossings.

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- Section: Science
- Country: China
- Published: 2026-10-13T01:40:12+00:00
- Updated: 2026-10-13T01:40:12+00:00
- Source review period: 2026-10-09
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To grow high-purity TiAs single crystals, the team used iodine-assisted chemical vapour transport from a polycrystalline precursor. X-ray diffraction and energy-dispersive spectroscopy checked structure and composition; Raman measurements examined vibrational modes, while angular magnetotransport probed directional response. ARPES data were compared with calculated three-dimensional bands.

Polarized Raman spectroscopy identified four Raman-active modes consistent with hexagonal symmetry. ARPES and first-principles calculations indicated symmetry-protected degeneracies at the Brillouin-zone boundary and a Van Hove saddle point about 0.5 eV below the Fermi level. Measured angular magnetoresistance showed twofold anisotropy. The results establish TiAs as a topological-semimetal research platform, not a device demonstration.

## Data

### Measurements reported by the study

The table reports only findings within this study’s experimental or model scope.

Methodology: Quantity and scope are taken from the methods and results of the first arXiv version dated 9 October 2026; they should not be generalized beyond the study.

| Reported study quantity | Value | Study scope |
|---|---|---|
| Raman-active optical phonon modes identified | 4 | A1g, E1g and two E2g modes assigned in polarized Raman measurements on experimental TiAs crystals, consistent with calculations. |

Sources: <https://arxiv.org/abs/2610.12925> · Download data: [JSON](https://newsverum.com/api/v1/articles/hexagonal-tias-crystals-symmetry-enforced-topology-2026/data/study-measurements?lang=en&format=json) · [CSV](https://newsverum.com/api/v1/articles/hexagonal-tias-crystals-symmetry-enforced-topology-2026/data/study-measurements?lang=en&format=csv)

## Sources

- [arXiv](<https://arxiv.org/abs/2610.12925>) (Source checked: 2026-10-13; Published: 2026-10-09)

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