In few research reports, the sound velocity anomaly in manganite has been taken as a proof of the observation of charge ordering and the temperature where anomaly has been observed (called charge ordering transition temperature (TCO)).
My question: Is it really so, or is the anomaly just an indication of diverging lattice degrees of freedom at that temperature?
As I understand, the diverging of the lattice degrees of freedom can occur due to many reasons like any type of structural/magnetic/electronic phase transition which can modify the lattice structure in a strongly correlated material at that temperature and thus can lead to an anomaly in sound velocity.
Dear Syed, according to my knowledge, the anomaly of the longitudinal wave sound velocity may mean a structural transition of solids. And the transition may be driven by the transfer of electrons among different bands at electronic scale, and mediated by dislocations, voids and so on at atomic scale.
There is a close relation between the charge ordering , e.g., formation of a charge-density wave and the anomaly in phonon dispersion law (vanishing of a certain mode-soft mode) called the Kohn anomaly . The phenomenon is a signature of the metal-insulator transition at structural phase transition in D=1,2. Kohn anomaly and charge density wave are complementary phenomena, in phonon and electron picture of the interacting electron-phonon system, related to the structural phase transition , or the metal-insulator transition respectively...
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