Coupling of electronic transition to ferroelectric order in a 2D semiconductor
A ferroelectric material often exhibits a soft transverse optical (TO) phonon mode which governs its phase transition. Charge coupling to this ferroelectric soft mode may further mediate emergent physical properties, including superconductivity and defect tolerance in semiconductors. However, direct experimental evidence for such coupling is scarce. Here we show that a photogenerated coherent phonon couples strongly to the electronic transition above the bandgap in the van der Waals (vdW) two-dimensional (2D) ferroelectric semiconductor NbOI<sub>2</sub>. Using terahertz time-domain spectroscopy and first-principles calculations, we identify this mode as the TO phonon responsible for ferroelectric order. This exclusive coupling occurs only with the above-gap electronic transition and is absent in the valence band as revealed by resonant inelastic X-ray scattering. Our findings suggest a new role of the soft TO phonon mode in electronic and optical properties of ferroelectric semiconductors.
Authors
- Yinming Shao (ORCID: https://orcid.org/0000-0002-2891-0028)
- David R. Reichman (ORCID: https://orcid.org/0000-0002-5265-5637)
- Chun‐Ying Huang (ORCID: https://orcid.org/0000-0001-6757-113X)
- Connor A. Occhialini (ORCID: https://orcid.org/0000-0002-2133-5155)
- Michael E. Ziebel (ORCID: https://orcid.org/0000-0003-1857-8292)
- Taketo Handa (ORCID: https://orcid.org/0000-0002-9171-5364)
- Nicholas Olsen (ORCID: https://orcid.org/0000-0003-1606-8707)
- Jonathan Pelliciari (ORCID: https://orcid.org/0000-0003-1508-7746)
- D. N. Basov (ORCID: https://orcid.org/0000-0001-9785-5387)
- Abhay N. Pasupathy (ORCID: https://orcid.org/0000-0002-2744-0634)
- Daniel G. Chica (ORCID: https://orcid.org/0000-0001-8616-9365)
- Valentina Bisogni (ORCID: https://orcid.org/0000-0002-7399-9930)
- Matthew Y. Sfeir (ORCID: https://orcid.org/0000-0001-5619-5722)
- Guiying He (ORCID: https://orcid.org/0000-0002-4009-2590)
- Xavier Roy (ORCID: https://orcid.org/0000-0002-8850-0725)
- Zhi‐Hao Cui (ORCID: https://orcid.org/0000-0002-7389-4063)
- Xiaoyang Zhu (ORCID: https://orcid.org/0000-0002-2090-8484)
- Morgan Thinel (ORCID: https://orcid.org/0000-0002-1453-4594)
- Yufeng Liu (ORCID: https://orcid.org/0000-0002-2733-7733)
Institutions
- The Graduate Center, CUNY (US)
- Pennsylvania State University (US)
- City University of New York (US)
- Brookhaven National Laboratory (US)
- CUNY Advanced Science Research Center (US)
- Columbia University (US)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-02-23
- DOI
- https://doi.org/10.1038/s41467-025-57061-9
- Citations
- 5
- Primary Topic
- 2D Materials and Applications
- Type
- article
- Field-Weighted Citation Impact
- 2.59
Funders
- National Science Foundation
- U.S. Department of Energy
- Air Force Office of Scientific Research
- Army Research Office