Raman phonons in the ferroelectric-like metal LiOsO3

Abstract

© 2016 American Physical Society. The novel ferroelectric-like structural transition observed in metallic LiOsO3 [Y. Shi et al., Nat. Mater. 12, 1024 (2013)], has invoked many theoretical and experimental interests. In this work, we have performed polarized and temperature-dependent Raman scattering measurements on high-quality single crystal LiOsO3 and identified Raman-active modes in both centrosymmetric phase (300 K, R3¯c) and noncentrosymmetric phase (10 K, R3c). Only four phonon peaks are observed in the former phase, while there are 12 peaks in the latter phase because of the reduction of crystal symmetry. With the help of careful symmetry analysis and first-principles calculations, we can make a systematic assignment for the observed Raman modes in both phases. The significant changes in linewidth and the continuous evolution of Raman frequencies with temperatures were observed for the Eg modes around the transition temperature, which suggests that the ferroelectric-like structural transition is a continuous order-disorder transition. The result sheds light on the coexistence of ferroelectricity and metallicity in the compound.