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<p>We use time- and angle-resolved photoemission spectroscopy (TR-ARPES) combined with density functional theory to investigate ultrafast carrier dynamics in low-symmetry layered semiconducting PdSe<sub>2</sub>. The indirect bandgap is determined to be 0.55 eV. Following photoexcitation above this gap, we resolve a valence band shift and broadening, both lasting less than a picosecond, consistent with bandgap renormalization and carrier scattering, indicative of strong many-body interactions. Subsequently, hot carriers populate the conduction band minimum and are captured by defect states. A surface photovoltage (SPV) of ~67 meV emerges, persisting for over 50 ps, driven by defect-assisted charge separation. The formation of native vacancies, promoted by the low-symmetry lattice, likely gives rise to the mid-gap states responsible for this long-lived SPV response. Detailed analysis of TR-ARPES spectra disentangles the contributions of bandgap renormalization, carrier scattering, defect states, and SPV. These findings establish PdSe<sub>2</sub> as a prototypical layered quantum material exhibiting exotic photoresponses on ultrafast timescales.</p>

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Photoinduced electronic band dynamics and defect-mediated surface potential evolution in PdSe2

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月12日

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  • Omar Abdul-Aziz,
  • Manuel Tuniz,
  • Wibke Bronsch,
  • Fulvio Parmigiani,
  • Federico Cilento,
  • Daniel Wolverson,
  • Charles J. Sayers,
  • Giulio Cerullo,
  • Claudia Dallera,
  • Ettore Carpene,
  • Paul H. M. van Loosdrecht,
  • Hamoon Hedayat

摘要

We use time- and angle-resolved photoemission spectroscopy (TR-ARPES) combined with density functional theory to investigate ultrafast carrier dynamics in low-symmetry layered semiconducting PdSe2. The indirect bandgap is determined to be 0.55 eV. Following photoexcitation above this gap, we resolve a valence band shift and broadening, both lasting less than a picosecond, consistent with bandgap renormalization and carrier scattering, indicative of strong many-body interactions. Subsequently, hot carriers populate the conduction band minimum and are captured by defect states. A surface photovoltage (SPV) of ~67 meV emerges, persisting for over 50 ps, driven by defect-assisted charge separation. The formation of native vacancies, promoted by the low-symmetry lattice, likely gives rise to the mid-gap states responsible for this long-lived SPV response. Detailed analysis of TR-ARPES spectra disentangles the contributions of bandgap renormalization, carrier scattering, defect states, and SPV. These findings establish PdSe2 as a prototypical layered quantum material exhibiting exotic photoresponses on ultrafast timescales.