Combined Raman and infrared investigation of the insulator-to-metal transition in NiS(2-x)Se(x) compounds

Marini, C and Perucchi, A and Chermisi, D and Dore, P and Valentini, M and Topwal, D and Sarma, DD and Lupi, S and Postorino, P (2011) Combined Raman and infrared investigation of the insulator-to-metal transition in NiS(2-x)Se(x) compounds. In: Physical Review B: Condensed Matter and Materials Physics, 84 (23).

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Abstract

Ambient-condition Raman spectra were collected in the strongly correlated NiS(1-x)Se(x) pyrite (0 <= x <= 1.2). Two samples (x = 0 and x = 0.55) were studied as a function of pressure up to 10 GPa, and for the x = 0.55 sample the pressure dependence of the infrared reflectivity was also measured (0-10 GPa). This gave a complete picture of the optical response of that system on approaching the metallic state both by application of pressure and/or by Se alloying, which corresponds to a volume expansion. A peculiar nonmonotonic (V-shaped) volume dependence was found for the quasiparticle spectral weight of both pure and Se-doped compounds. In the x = 0.55 sample the vibrational frequencies of the chalcogen dimer show an anomalous volume dependence on entering the metallic phase. The abrupt softening observed, particularly significant for the Se-Se pair, indicates the relevant role of the softness of the Se-Se bond as previously suggested by theoretical calculations.

Item Type:	Journal Article
Publication:	Physical Review B: Condensed Matter and Materials Physics
Publisher:	The American Physical Society
Additional Information:	Copyright of this article belongs to The American Physical Society.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	27 Jan 2012 06:27
Last Modified:	27 Jan 2012 06:27
URI:	http://eprints.iisc.ac.in/id/eprint/43150

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