Pressure-induced quenching of the Jahn-Teller distortion and insulator-to-metal transition in LaMnO3 - art. no. 125501

LaMnO3 was studied by synchrotron x-ray diffraction, optical spectroscopies , and transport measurements under pressures up to 40 GPa. The cooperative Jahn-Teller (JT) distortion is continuously reduced with increasing pressur e. There is strong indication that the JT effect and the concomitant orbita l order are completely suppressed above 18 GPa. The system, however, retain s its insulating state to similar to 32 GPa, where it undergoes a bandwidth -driven insulator-metal transition. Delocalization of electron states, whic h suppresses the JT effect but is insufficient to make the system metallic, appears to be a key feature of LaMnO3 at 20-30 GPa.