LOW-ENERGY RAMAN CONTINUUM IN OVERDOPED Y 1− xCa xBa 2Cu 3O 7 FILMS

• Published in: The Journal of physics and chemistry of solids Vol. 59; no. 10; pp. 1958 - 1961
• Main Authors: Bock, A., Dassharma, R., Ostertun, S., Subke, K.-O.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1998
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/S0022-3697(98)00143-7

We investigate Y 1− x Ca x Ba 2Cu 3O 7 films on SrTiO 3(100) substrates which are overdoped due to high oxygen contents and Ca substitution. The good in-plane orientation of the c-axis-oriented films allows us to study excitations with A 1g and B 1g symmetry. Our analysis reveals that at high doping the B 1g Raman-active phonon at 340 cm −1 behaves significantly differently from what has been observed so far, showing vanishing softening as well as strong broadening and no increasing intensity below T c. The observed behavior correlates with the fact that the energy of the so-called “2 Δ peak” that forms out of the continuum in B 1g symmetry is below the phonon energy at higher doping.