Plasmon Behavior at the Charge-Density-Wave Onset in 2H-TaSe2

The thermoreflectance of 2H-TaSe2 in the neighborhood of plasmon resonance near 1 eV, as a function of temp., was studied. A close inspection of the dielectric response as a function of frequency and temp. shows that optical transitions disappear in the 0.2-0.8 eV region in correspondence with the w...

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Bibliographic Details
Published in:Physical review. B, Condensed matter Condensed matter, 1979-01, Vol.20 (6), p.2217-2227
Main Authors: Campagnoli, G, Gustinetti, A, Stella, A, Tosatti, E
Format: Article
Language:English
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Summary:The thermoreflectance of 2H-TaSe2 in the neighborhood of plasmon resonance near 1 eV, as a function of temp., was studied. A close inspection of the dielectric response as a function of frequency and temp. shows that optical transitions disappear in the 0.2-0.8 eV region in correspondence with the weakening of CDW upon heating, while new intraband ( < 0.2 eV) and interband ( > 1 eV) transitions replace them. A theory of plasmon shift caused by the new CDW periodicity is developed, and applied the present case, by means of a model umklapp response. The results show that the shift is chiefly due to the presence of the new CDW transitions in the 3 x 3 band structure. The temp.-induced change of optical response at the onset is also found to be smooth and broad with temp. unlike that of other properties, like specific heat, which exhibit a clear critical behavior.26 refs.--AA
ISSN:0163-1829
DOI:10.1103/PhysRevB.20.2217