Nature of the 175-180 cm−1 Raman Feature in Altermagnetic α-MnTe
Abstract
The 175 cm−1 Raman mode in α-MnTe has long been assigned to the material's only symmetry-allowed phonon (E2g), yet first-principles calculations consistently place this mode below 100 cm−1. Recent works have offered three competing explanations for the discrepancy: a weak symmetry-lowering (D6h→ D3h) phonon, an electronic plasmon arising from intrinsic hole self-doping, or an extrinsic MnTe2 impurity signature. Here we resolve this controversy using stoichiometry-controlled molecular beam epitaxy (MBE). We deliberately vary the fraction of pyrite-type MnTe2 secondary phase relative to the α-MnTe matrix. Across this series, the 175 cm−1 mode tracks the presence of MnTe2 essentially one-to-one -- present wherever MnTe2 is detectable, absent in stoichiometric, single-phase α-MnTe at nominal LASER powers. When LASER power is ramped up, an additional mode emerges in MnTe as well positioned close to ≈ 175 cm−1; our detailed temperatures dependendent Raman analysis identifies the LASER power scorched region close to a distorted MnTe phase, confirmed via transmission electron microscopy. This direct, growth-controlled correlation identifies the mode as an extrinsic MnTe2 impurity signature or as a distorted MnTe feature, rather than an intrinsic phonon or plasmon feature, providing a practical diagnostic for phase purity in MBE-grown α-MnTe and clarifying which Raman features can be reliably attributed to the intrinsic altermagnetic phase.
Related
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- Spontaneous Circular Dichroism and Memory Effect from Surface Defects in Altermagnetic MnTe
- Magnetic Field Control of the Néel Vector and Magnon Visibility in Altermagnetic MnTe
- Intertwined ferromagnetic and altermagnetic orders in Cr-doped MnTe
- Imaging Surface Magnetization in Altermagnetic MnTe Films
BibTeX
@misc{bhardwaj2026nature,
title = {{Nature of the 175-180 cm$^-1$ Raman Feature in Altermagnetic $α$-MnTe}},
author = {Pankaj Bhardwaj and Rajib Sarkar and Naresh Shyaga and Subhransu Kumar Negi and Kartick Biswas and Susmita Jana and Pavan Nukala and B. R. K. Nanda and Dhavala Suri},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.39108},
eprint = {2609.39108},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.39108},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - Nature of the 175-180 cm^−1 Raman Feature in Altermagnetic α-MnTe
AU - Pankaj Bhardwaj
AU - Rajib Sarkar
AU - Naresh Shyaga
AU - Subhransu Kumar Negi
AU - Kartick Biswas
AU - Susmita Jana
AU - Pavan Nukala
AU - B. R. K. Nanda
AU - Dhavala Suri
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.39108
UR - https://arxiv.org/abs/2609.39108
AB - The 175 cm^−1 Raman mode in α-MnTe has long been assigned to the material's only symmetry-allowed phonon (E_2g), yet first-principles calculations consistently place this mode below 100 cm^−1. Recent works have offered three competing explanations for the discrepancy: a weak symmetry-lowering (D_6h→ D_3h) phonon, an electronic plasmon arising from intrinsic hole self-doping, or an extrinsic MnTe_2 impurity signature. Here we resolve this controversy using stoichiometry-controlled molecular beam epitaxy (MBE). We deliberately vary the fraction of pyrite-type MnTe_2 secondary phase relative to the α-MnTe matrix. Across this series, the 175 cm^−1 mode tracks the presence of MnTe_2 essentially one-to-one -- present wherever MnTe_2 is detectable, absent in stoichiometric, single-phase α-MnTe at nominal LASER powers. When LASER power is ramped up, an additional mode emerges in MnTe as well positioned close to ≈ 175 cm^−1; our detailed temperatures dependendent Raman analysis identifies the LASER power scorched region close to a distorted MnTe phase, confirmed via transmission electron microscopy. This direct, growth-controlled correlation identifies the mode as an extrinsic MnTe_2 impurity signature or as a distorted MnTe feature, rather than an intrinsic phonon or plasmon feature, providing a practical diagnostic for phase purity in MBE-grown α-MnTe and clarifying which Raman features can be reliably attributed to the intrinsic altermagnetic phase.
ER -