Phonon softening and "forbidden" mode observed by Raman scattering in Na0.5CoO2 (2008)
Zhang, Q. M., An, M., Yuan, S. K., Wu, Y., Wu, D., Luo, J. L., ...
Polarized Raman scattering measurements have been performed on Na0.5CoO2 single crystal from 8 to 305 K. Both the A1g and E1g phonon modes show a softening below Tc1 ~ 83 K. Additionally, the A1g...