Experimental and theoretical study of anomalous temperature dependence of phonons in Y2Ti2 O7 pyrochlore

Verma, PK and Saha, S and Muthu, DVS and Singh, S and Suryanarayanan, R and Revcolevschi, A and Waghmare, UV and Sood, AK and Krishnamurthy, HR (2022) Experimental and theoretical study of anomalous temperature dependence of phonons in Y2Ti2 O7 pyrochlore. In: Physical Review B, 106 (14).

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Abstract

We present Raman spectroscopic as well as first-principles theoretical studies of the temperature dependence of phonon spectra in the pyrochlore Y2Ti2O7. Our experimental results show that the frequencies of several phonons display anomalous softening upon cooling. Our theoretical calculations of the temperature dependence, via phonon self-energy corrections arising from cubic anharmonic interactions, lead to such anomalies but only for a couple of high-frequency phonon modes. Our work strongly supports the suggestion that anharmonic phonon-phonon interactions are strong in the pyrochlore titanates and that they are responsible for the phonon anomalies observed. The strong anharmonic effects are likely due to the presence of the vacant Wyckoff sites and the shifts of the oxygen atoms from their actual positions in the pyrochlore lattice. However, the theoretical calculations fail to explain the anomalous behavior of low and intermediate frequency modes observed in our experiments. It seems likely that a much more sophisticated, perhaps nonperturbative, treatment of the anharmonic interactions will be required for a full explanation of the anomalies.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	The copyright for this article belongs to American Physical Society.
Keywords:	Binary alloys; Calculations; Temperature distribution; Titanium alloys, Anharmonic interaction; First principles; High frequency phonons; Phonon spectrum; Pyrochlores; Raman spectroscopic; Self-energy corrections; Temperature dependence; Theoretical calculations; Theoretical study, Phonons
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	04 Nov 2022 09:22
Last Modified:	04 Nov 2022 09:22
URI:	https://eprints.iisc.ac.in/id/eprint/77765

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