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<p>The two-dimensional bromine-terminated MXene Hf<sub>2</sub>CBr<sub>2</sub> is investigated using first-principles density functional theory calculations incorporating spin–orbit coupling, GGA + U formalism, and time-dependent DFT optical analysis. Structural optimisation confirms a stable hexagonal Br–Hf–C–Hf–Br layered configuration with preserved inversion symmetry. The electronic band structure reveals strong SOC-driven band inversion and a nontrivial Z<sub>2</sub> = 1 topological invariant, establishing Hf<sub>2</sub>CBr<sub>2</sub> as a quantum spin Hall insulator with protected helical edge states suitable for dissipationless spin transport. Projected density of states analysis shows dominant Hf 5d orbital contributions near the Fermi level, hybridised with C 2p and Br 4p states. Spin-orbit coupling and the underlying topological band inversion enable potential spin-textured optical responses, particularly under circularly polarised light or in helical edge-state configurations, highlighting the material’s promise for topological photonics and spin-optoelectronics. The material also exhibits strong plasmonic resonances and broadband optical activity extending from visible to ultraviolet energies, highlighting its potential for spintronics, topological photonics, and UV optoelectronic applications.</p>

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Z2 topological insulation and intrinsic spin-optical dichroism in two-dimensional Hf2CBr2 MXene: first-principles evidence for quantum spin hall spintronics and topological UV photonics

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Sayongita Singh,
  • V. R. Patel,
  • N. Deshmukh,
  • A. N. Deshmukh,
  • Mitesh B. Solanki

摘要

The two-dimensional bromine-terminated MXene Hf2CBr2 is investigated using first-principles density functional theory calculations incorporating spin–orbit coupling, GGA + U formalism, and time-dependent DFT optical analysis. Structural optimisation confirms a stable hexagonal Br–Hf–C–Hf–Br layered configuration with preserved inversion symmetry. The electronic band structure reveals strong SOC-driven band inversion and a nontrivial Z2 = 1 topological invariant, establishing Hf2CBr2 as a quantum spin Hall insulator with protected helical edge states suitable for dissipationless spin transport. Projected density of states analysis shows dominant Hf 5d orbital contributions near the Fermi level, hybridised with C 2p and Br 4p states. Spin-orbit coupling and the underlying topological band inversion enable potential spin-textured optical responses, particularly under circularly polarised light or in helical edge-state configurations, highlighting the material’s promise for topological photonics and spin-optoelectronics. The material also exhibits strong plasmonic resonances and broadband optical activity extending from visible to ultraviolet energies, highlighting its potential for spintronics, topological photonics, and UV optoelectronic applications.