Anomalous pressure dependence of phonon line widths in metallic pyrochlore iridates (Eu 1-x Bi x) 2 Ir 2 O 7 : crossover from incoherent to coherent metal

Thomas, A and Telang, P and Rout, D and Mishra, K and Pal, A and Muthu, DVS and Kumar, PSA and Singh, S and Sood, AK (2023) Anomalous pressure dependence of phonon line widths in metallic pyrochlore iridates (Eu 1-x Bi x) 2 Ir 2 O 7 : crossover from incoherent to coherent metal. In: Pramana - Journal of Physics, 97 (3).

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Abstract

Pyrochlore iridate (Eu 2 Ir 2 O 7) shows an interesting metallic phase, termed as incoherent metal, above the metal–insulator transition temperature, with high resistivity and positive temperature coefficient of resistivity (TCR). On increasing the pressure, there is a crossover at pressure P* to a coherent metal phase with positive TCR. We have investigated this crossover using high-pressure Raman spectroscopy and X-ray diffraction for a series of samples (Eu 1-x Bi x) 2 Ir 2 O 7 (x = 0, 0.02, 0.035 and 0.1) up to ∼ 20 GPa. X-ray diffraction data show a clear change in the pressure dependence of Ir–Ir bond distance at P*. The line width of the A 1g phonon shows an anomalous decrease with pressure up to P*, without significant change in the line width of the other three Raman modes with symmetries T2g1 , Eg and T2g2 . We attribute these results to the decreasing contribution of electron–phonon coupling in the incoherent metal till P*.

Item Type:	Journal Article
Publication:	Pramana - Journal of Physics
Publisher:	Springer
Additional Information:	The copyright for this article belongs to the Springer.
Keywords:	Metal insulator transition; Phonons; X ray diffraction, 61.05.; 71.38.; 78.30.; 81.40.; Cp; Er; Phonon renormalization; Pyrochlores; Renormalization; Vw; �k, Temperature
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	04 Nov 2023 05:06
Last Modified:	04 Nov 2023 05:06
URI:	https://eprints.iisc.ac.in/id/eprint/83130

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