Probing IrTe2 crystal symmetry by polarized Raman scattering

Article

关键词: BAND-STRUCTURE;    TRANSITION;    BONDS;   

DOI  :  10.1103/PhysRevB.89.224301

来源: SCIE

【 摘 要 】

Polarized Raman scattering measurements on IrTe2 single crystals carried out over the 15-640 K temperature range, and across the structural phase transition, reveal different insights regarding the crystal symmetry. In the high temperature regime three Raman active modes are observed at all of the studied temperatures above the structural phase transition, rather than two as predicted by the factor group analysis for the assumed P (3) over bar m1 symmetry. This indicates that the actual symmetry of the high temperature phase is lower than previously thought. The observation of an additional E-g mode at high temperature can be explained by doubling of the original trigonal unit cell along the c axis and within the P (3) over bar c1 symmetry. In the low temperature regime (below 245 K) the other Raman modes appear as a consequence of the symmetry lowering phase transition and the corresponding increase of the primitive cell. All of the modes observed below the phase transition temperature can be assigned within the monoclinic crystal symmetry. The temperature dependence of the Raman active phonons in both phases is mainly driven by anharmonicity effects. The results call for reconsideration of the crystallographic phases of IrTe2.

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