Spin-charge-lattice coupling in YBaCuFeO5: Optical properties and first-principles calculations

H W Chen; Y-W Chen; J-L Kuo; Y C Lai; F C Chou; C H Du; H L Liu

doi:10.1038/s41598-019-39031-6

Spin-charge-lattice coupling in YBaCuFeO₅: Optical properties and first-principles calculations

Sci Rep. 2019 Mar 1;9(1):3223. doi: 10.1038/s41598-019-39031-6.

Authors

H W Chen¹, Y-W Chen², J-L Kuo², Y C Lai^{3

4}, F C Chou³, C H Du⁴, H L Liu⁵

Affiliations

¹ Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan.
² Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
³ Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan.
⁴ Department of Physics, Tamkang University, Tamsui, New Taipei City, 25137, Taiwan.
⁵ Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan. hliu@ntnu.edu.tw.

Abstract

We combined spectroscopic ellipsometry, Raman scattering spectroscopy, and first-principles calculations to explore the optical properties of YBaCuFeO₅ single crystals. Measuring the optical absorption spectrum of YBaCuFeO₅ at room temperature revealed a direct optical band gap at approximately 1.41 eV and five bands near 1.69, 2.47, 3.16, 4.26, and 5.54 eV. Based on first-principles calculations, the observed optical excitations were appropriately assigned. Analysis of the temperature dependence of the band gap indicated anomalies in antiferromagnetic phase transition at 455 and 175 K. Additionally, a hardening in the frequency of the E_g phonon mode was observed at 175 K. The value of the spin-phonon coupling constant was 15.7 mRy/Å². These results suggest a complex nature of spin-charge-lattice interactions in YBaCuFeO₅.