Fig. 3: Phonon dispersion calculation of the high-temperature tetragonal structure.
From: Dynamics of collective modes in an unconventional charge density wave system BaNi2As2
Phonon dispersion along the a [100] and b [101] directions. The dashed red vertical line in a signifies the CDW wave-vectors of the incommensurate CDW (I-CDW) while the line in b corresponds to the CDW wave-vectors of the commensurate CDW (C-CDW) order. The dashed horizontal lines indicate the low-temperature frequencies of the observed modes. Note that calculations show an instability in an optical branch quite close to the critical wavevector of the I-CDW (see also Methods).
