Experimental evidence for the dynamic Jahn-Teller effect in ${\mathrm{La}}_{0.65}$${\mathrm{Ca}}_{0.35}$Mn${\mathrm{O}}_3$

Recently, it has been argued that a strong electron-phonon interaction arising from the Jahn-Teller splitting of the outer Mn $d$ level plays a crucial role in understanding the nonmetal-to-metal transition observed in the ${\mathrm{La}}_{1-x}{A}_x\mathrm{Mn}{\mathrm{O}}_3(A=\mathrm{C}\mathrm{a},\mathrm{S}\mathrm{r},\mathrm{B}\mathrm{a})$ system. We show, by neutron powder diffraction, that ${\mathrm{La}}_{0.65}$${\mathrm{Ca}}_{0.35}$Mn${\mathrm{O}}_3$ exhibits an anomalous volume and oxygen/manganese displacement change around $T_c$, in qualitative agreement with the theoretical prediction.