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Updated: Jul 16, 2026

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Symmetry-Breaking and Selection-Rule Relaxation in CVD-Grown Hexagonal FeTe2 Probed by Angle- and Helicity-Resolved
Ikhwan Nur Rahman1, Gwang Hwi An1,2, Min Choi1
1Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea.
Abstract:
Symmetry plays a central role in determining the vibrational and electronic properties of two-dimensional transition-metal chalcogenides. However, in materials grown by chemical vapor deposition (CVD), local structural imperfections can modify the effective symmetry, and their impact on phonon selection rules remains insufficiently understood. Here, we probe symmetry-dependent phonons in CVD-grown hexagonal-FeTe2 using polarization-resolved Raman spectroscopy with both linear and circular configurations. Two prominent modes, at 135 cm-1 and 155 cm-1, show contrasting behavior: The peak at 135 cm-1 follows the expected selection rules, whereas the peak at 155 cm-1 exhibits pronounced deviations, including anomalous angular response and finite intensity in forbidden helicity channels. These results reveal a breakdown of Raman selection rules, which we attribute to local symmetry reduction arising from structural and chemical nonidealities, including oxygen-related surface chemistry. Temperature-dependent measurements show no evidence of spin-phonon coupling, indicating a nonmagnetic origin. Our findings establish polarization-resolved Raman spectroscopy as a sensitive probe of symmetry and structural quality, providing practical insight into how growth-induced imperfections shape phonon behavior in synthesized metal chalcogenides.
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