Electronic structure and lattice dynamics of Ba2CuTeO6
Yun-Chen Chung1*, Sunil K. Karna2, Fan-Cheng Chou2, Hsiang-Lin Liu1
1Department of Physics, National Taiwan Normal University, Taipei, Taiwan
2Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
* Presenter:Yun-Chen Chung, email:coldlizem@gmail.com
We combined spectroscopic ellipsometry and Raman scattering measurements to explore the electronic structure and lattice dynamics in Ba2CuTeO6 single crystals. The room temperature optical absorption spectrum of Ba2CuTeO6 exhibits four bands at approximately 1.45, 3.43, 4.65 and 5.79 eV. The lowest energy optical absorption was assigned to on-site Cu2+ d-d transition. The other higher energy optical absorptions were attributed to charge-transfer transitions between O 2p and Te 5p states. The room temperature Raman scattering spectrum of Ba2CuTeO6 shows sixteen phonon modes at approximately 85, 97 104, 118, 160, 194, 380, 196, 404, 409, 492, 568, 574, 606, 678 and 751 cm-1. With decreasing temperature across 287 K, which is the structural phase transition from monoclinic to triclinic phase, additional phonon modes appear at approximately 124 and 128 cm-1. Upon further cooling across 75 and 15 K, which are the short-range and long-range antiferromagnetic phase transitions, 124, 128 and 163 cm-1 phonon modes exhibit a softening, suggesting a coupling between the magnetic and lattice degrees of freedom.

Keywords: strongly correlated electrons, spin-phonon coupling