The Origin of the Observed Raman Peaks in α-MnTe
Abstract
The Raman spectrum of the room-temperature altermagnet α-MnTe is reported to contain unassigned peaks at 120(3) cm−1 and 140(3) cm−1, absent from the predicted phonon spectrum of the material. This has generated considerable debate within the altermagnet community and necessitates urgent resolution. This work establishes that these peaks, together with the 90(5) cm−1 peak that matches a theoretically predicted mode, are all extrinsic, originating from elemental tellurium formed during air exposure of the surface. Raman spectra of MBE-grown thin films show that these peaks closely match those of elemental tellurium, emerge soon after air exposure, and are absent in AlOx-capped films. X-ray photoelectron spectroscopy shows that air exposure breaks Mn--Te bonds and oxidizes Mn within a minute. Cross-sectional scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy reveals that the oxidation leads to Mn out-diffusion, forming a few-nanometer-thick oxide layer above a buried, Te-enriched region, likely responsible for the anomalous Raman peaks. Additionally, no sample exhibited the 175 cm−1 Raman peak which is commonly attributed to MnTe2. The aggressive surface oxidation and associated elemental Te formation in MnTe have important implications for any surface-sensitive and optical characterization of MnTe (and other similar Te-containing materials) involving even the briefest air exposure.
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BibTeX
@misc{azam2026origin,
title = {{The Origin of the Observed Raman Peaks in α-MnTe}},
author = {Nurul Azam and Syed Mohammad Shahed and Liam T. Schmidt and Sara Bey and Oksana Yastrubchak and Maria F. Munoz and Riccardo Torsi and Thi Hai Yen Pham and Dushyanthini Balasundaram and Resham Babu Regami and Wentao Liang and Imrankhan Mulani and Matthew Matzelle and Vineet Kumar Sharma and Sougata Mardanya and Sugata Chowdhury and Nirmal Ghimire and Patrick M. Vora and Angela R. Hight Walker and Xinyu Liu and Badih A. Assaf and Arun Bansil and Alberto De la Torre and Swastik Kar},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.19467},
eprint = {2609.19467},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.19467},
}
RIS
TY - UNPB
TI - The Origin of the Observed Raman Peaks in α-MnTe
AU - Nurul Azam
AU - Syed Mohammad Shahed
AU - Liam T. Schmidt
AU - Sara Bey
AU - Oksana Yastrubchak
AU - Maria F. Munoz
AU - Riccardo Torsi
AU - Thi Hai Yen Pham
AU - Dushyanthini Balasundaram
AU - Resham Babu Regami
AU - Wentao Liang
AU - Imrankhan Mulani
AU - Matthew Matzelle
AU - Vineet Kumar Sharma
AU - Sougata Mardanya
AU - Sugata Chowdhury
AU - Nirmal Ghimire
AU - Patrick M. Vora
AU - Angela R. Hight Walker
AU - Xinyu Liu
AU - Badih A. Assaf
AU - Arun Bansil
AU - Alberto De la Torre
AU - Swastik Kar
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.19467
UR - https://arxiv.org/abs/2609.19467
AB - The Raman spectrum of the room-temperature altermagnet α-MnTe is reported to contain unassigned peaks at 120(3) cm^−1 and 140(3) cm^−1, absent from the predicted phonon spectrum of the material. This has generated considerable debate within the altermagnet community and necessitates urgent resolution. This work establishes that these peaks, together with the 90(5) cm^−1 peak that matches a theoretically predicted mode, are all extrinsic, originating from elemental tellurium formed during air exposure of the surface. Raman spectra of MBE-grown thin films show that these peaks closely match those of elemental tellurium, emerge soon after air exposure, and are absent in AlO_x-capped films. X-ray photoelectron spectroscopy shows that air exposure breaks Mn--Te bonds and oxidizes Mn within a minute. Cross-sectional scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy reveals that the oxidation leads to Mn out-diffusion, forming a few-nanometer-thick oxide layer above a buried, Te-enriched region, likely responsible for the anomalous Raman peaks. Additionally, no sample exhibited the 175 cm^−1 Raman peak which is commonly attributed to MnTe_2. The aggressive surface oxidation and associated elemental Te formation in MnTe have important implications for any surface-sensitive and optical characterization of MnTe (and other similar Te-containing materials) involving even the briefest air exposure.
ER -