Ultrafast dynamics in the Lifshitz-type 5d pyrochlore antiferromagnet Cd2Os2O7

Abstract

We investigate the ultrafast dynamics of Cd2Os2O7, a prototype material showing a Lifshitz-type transition as a function of temperature. In the paramagnetic metallic state, the photoreflectivity shows a subpicosecond relaxation, followed by a featureless small offset. In the antiferromagnetic state slightly below T-N, however, the photoreflectivity resurges over hundreds of picoseconds, which goes beyond the usual realm of the effective-temperature model. Our observations are consistent with the Lifshitz phase transition of Cd2Os2O7 driven by the evolution of the local magnetic moment. ©2019 American Physical Society