Reflectivity studies of Ti- and Ta-dichalcogenides: Phonons |
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| Authors: | G Lucovsky WY Liang RM White KR Pisharody |
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| Institution: | Xerox Palo Alto Research Center, Palo Alto, CA 94304, U.S.A.;W.W. Hansen Laboratories of Physics, Stanford University, Stanford, CA 94305, U.S.A. |
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| Abstract: | The i.r.-spectra of the 1T phases of TiS2, TiSe2, TaS2 and TaSe2 reveal features attributed to large free carrier densities and to i.r.-active longwavelength phonons. We find a single phonon in TiS2, TiSe2 and TaS2, but six phonons in TaSe2, The oscillator strengths are significantly higher in the Ti-compounds yielding large values of the infrared effective charge, ～6e, and electron-phonon coupling constant, 0.4–1.0. The observation of many modes in TaSe2 is attributed to a superlattice distortion driven by a charge density wave. |
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