Anomalous phonon Grüneisen parameters in semiconductor Ta$_2$NiS$_5$
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arXiv
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| Format: | Preprint |
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2024
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| author | Ye, Mai Lacmann, Tom Frachet, Mehdi Vinograd, Igor Garbarino, Gaston Maraytta, Nour Merz, Michael Heid, Rolf Haghighirad, Amir-Abbas Tacon, Matthieu Le |
| author_facet | Ye, Mai Lacmann, Tom Frachet, Mehdi Vinograd, Igor Garbarino, Gaston Maraytta, Nour Merz, Michael Heid, Rolf Haghighirad, Amir-Abbas Tacon, Matthieu Le |
| contents | Strain tuning is a powerful experimental method in probing correlated electron systems. Here we study the strain response of the lattice dynamics and electronic structure in semiconductor Ta$_2$NiS$_5$ by polarization-resolved Raman spectroscopy. We observe an increase of the size of the direct semiconducting band gap. Although the majority of the optical phonons show only marginal dependence to applied strain, the frequency of the two B$_{2g}$ phonon modes, which have quadrupolar symmetry and already anomalously soften on cooling under zero strain, increases significantly with tensile strain along the $a$ axis. The corresponding Grüneisen parameters are unusually large in magnitude and negative in sign. These effects are well captured by first-principles density functional theory calculations and indicate close proximity of Ta$_2$NiS$_5$ to a structural instability, similar to that encountered in excitonic insulator candidate Ta$_2$NiSe$_5$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2405_01455 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Anomalous phonon Grüneisen parameters in semiconductor Ta$_2$NiS$_5$ Ye, Mai Lacmann, Tom Frachet, Mehdi Vinograd, Igor Garbarino, Gaston Maraytta, Nour Merz, Michael Heid, Rolf Haghighirad, Amir-Abbas Tacon, Matthieu Le Strongly Correlated Electrons Materials Science Strain tuning is a powerful experimental method in probing correlated electron systems. Here we study the strain response of the lattice dynamics and electronic structure in semiconductor Ta$_2$NiS$_5$ by polarization-resolved Raman spectroscopy. We observe an increase of the size of the direct semiconducting band gap. Although the majority of the optical phonons show only marginal dependence to applied strain, the frequency of the two B$_{2g}$ phonon modes, which have quadrupolar symmetry and already anomalously soften on cooling under zero strain, increases significantly with tensile strain along the $a$ axis. The corresponding Grüneisen parameters are unusually large in magnitude and negative in sign. These effects are well captured by first-principles density functional theory calculations and indicate close proximity of Ta$_2$NiS$_5$ to a structural instability, similar to that encountered in excitonic insulator candidate Ta$_2$NiSe$_5$. |
| title | Anomalous phonon Grüneisen parameters in semiconductor Ta$_2$NiS$_5$ |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2405.01455 |