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Polarized far-infrared and Raman spectra of SrCuO2 single crystals

Z. V. Popović·M. J. Konstantinović·R. Gajić·C. Thomsen·U. Kuhlmann·A. Vietkin
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Abstract

We measured polarized far-infrared reflectivity and Raman scattering spectra of SrCuO$_2$ single crystals. The frequencies for infrared-active modes were determined using an oscillator-fitting procedure of reflectivity data. The Raman spectra were measured at different temperatures using several laser energies $ω_L$. In addition to eight of twelve Raman active modes, predicted by factor-group analysis, we observed a complex structure in the Raman spectra for polarization parallel to the {\bf c}-axis, which consists of Raman-allowed A$_g$ symmetry modes, and B$_{1u}$ LO infrared-active (Raman-forbidden) modes of the first and higher order as well as their combinations. The Raman-forbidden modes have a stronger intensity at higher $ω_L$ than the Raman-allowed ones. In order to explain this resonance effect, we measured the dielectric function and optical reflection spectra of SrCuO$_2$ in the visible range. We show that the Raman-allowed A$_g$ symmetry modes are resonantly enhanced when a laser energy is close to $E_0$, while Raman-forbidden (IR-active) modes resonate strongly for laser line energies close to the electronic transition of higher energy gaps.

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Z. V. Popović, M. J. Konstantinović, R. Gajić, C. Thomsen, U. Kuhlmann, A. Vietkin. 2000-10-16. Polarized far-infrared and Raman spectra of SrCuO2 single crystals. https://doi.org/10.1016/s0921-4534(00)01636-1

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