{
  "abstract": "Polarization sensitivity and limited tunability remain important challenges for high-Q terahertz (THz) metasurfaces based on quasi-bound states in the continuum (q-BICs), particularly when geometric perturbations are introduced to enable radiative coupling. Here, we numerically demonstrate a graphene-integrated all-dielectric THz metasurface that combines high-Q q-BIC resonances, polarization robustness, electrical tunability, and refractive-index sensing through a C4-symmetric supercell design. Each metamolecule consists of two orthogonal amorphous-silicon strips, in which a width perturbation δ introduces local geometric asymmetry and enables the symmetry-protected states to couple to free space, while the four metamolecules related by successive 90° rotations preserve the global C4 rotational symmetry. Two q-BIC modes are supported, with their Q factors exhibiting the characteristic inverse-square dependence on δ. Multipolar analysis reveals that the lower-frequency q-BIC is dominated by magnetic-quadrupole radiation, whereas the higher-frequency mode is primarily governed by toroidal-dipole radiation and exhibits weaker overall radiative leakage. Owing to the C4-symmetric arrangement, the resonance spectra remain nearly invariant for normally incident linearly polarized THz waves over polarization angles from 0° to 90°. Integration of monolayer graphene further enables continuous electrical modulation of the resonance contrast and Q factor by varying the Fermi level from 0 to 0.7 eV, while inducing only minor resonance-frequency shifts. For bulk refractive-index sensing, the two q-BIC modes achieve sensitivities of 345 and 475 GHz/RIU, with maximum figures of merit exceeding 800 and approaching 104, respectively. These results provide a versatile strategy for integrating polarization-robust high-Q resonances, electrical reconfigurability, and high-performance refractive-index sensing in THz metasurfaces.",
  "abstract_shown": true,
  "affiliations": [
    "School of Physics, Nanjing University of Science and Technology, Nanjing 210094, China"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Mingyu Geng"
    },
    {
      "affs": [
        0
      ],
      "name": "Qinghua Wang",
      "orcid": "0000-0002-7520-3449"
    },
    {
      "affs": [
        0
      ],
      "name": "Yunjing Ji"
    },
    {
      "affs": [
        0
      ],
      "name": "Jiancheng Lai"
    },
    {
      "affs": [
        0
      ],
      "name": "Zhenhua Li"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/28y077jfewbtg.bib",
  "cited_by": 0,
  "doi": "10.3390/nano16211377",
  "fulltext_url": null,
  "id": "28y077jfewbtg",
  "issns": [
    "2079-4991"
  ],
  "landing_url": "https://www.mdpi.com/2079-4991/16/21/1377",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2504|Metamaterials and Metasurfaces Applications"
    ]
  ],
  "openalex": "W7224114155",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-28",
  "publisher": "MDPI AG",
  "ris": "https://research.draconitic.com/paper/28y077jfewbtg.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:45Z",
      "native_id": "10.3390/nano16211377",
      "source": "crossref",
      "url": "https://www.mdpi.com/2079-4991/16/21/1377"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:2504|Metamaterials and Metasurfaces Applications",
      "subfield": "materials-polymers"
    }
  ],
  "title": "Polarization-Robust and Electrically Tunable Quasi-Bound States in the Continuum in C4-Symmetric Terahertz Metasurfaces for Refractive-Index Sensing",
  "title_text": "Polarization-Robust and Electrically Tunable Quasi-Bound States in the Continuum in C4-Symmetric Terahertz Metasurfaces for Refractive-Index Sensing",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:45Z",
  "url": "https://research.draconitic.com/paper/28y077jfewbtg",
  "venue": "Nanomaterials",
  "versions": []
}