A Raman study of the charge-density-wave state in A₀.₃MoO₃ (A = K, Rb)

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Sagar, Dodderi M. ; Fausti, D. ; Yue, S. ; Kuntscher, Christine A. ; van Smaalen, Sander ; van Loosdrecht, Paul H. M.:
A Raman study of the charge-density-wave state in A₀.₃MoO₃ (A = K, Rb).
In: New Journal of Physics. Bd. 10 (26 Februar 2008) Heft 2 . - 023043.
ISSN 1367-2630
DOI: https://doi.org/10.1088/1367-2630/10/2/023043

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Abstract

We report a comparative Raman spectroscopic study of the quasi-one-dimensional charge-density-wave (CDW) systems A 0.₃MoO₃ (A = K, Rb). Temperature- and polarization-dependent experiments reveal charge-coupled vibrational Raman features. The strongly temperature-dependent collective amplitudon modes in the two materials differ by about 3 cm −1 , thus revealing the role of the alkali atom. We discuss the observed vibrational features in terms of the CDW ground state accompanied by a change in the crystal symmetry. A frequency-kink in some modes seen in K0.₃MoO₃ between T = 80 and 100 K supports the first-order lock-in transition, unlike the case of Rb0.₃MoO₃. The unusually sharp Raman lines (limited by the instrumental response) at very low temperatures and their temperature evolution suggests that the decay of the low-energy phonons is strongly influenced by the presence of the temperature-dependent CDW gap.