Evolution of the magnetic and polaronic order of $\rm{Pr_{1/2}Ca_{1/2}MnO_3}$ following an ultrashort light pulse

TL;DR

This study simulates ultrafast light pulse effects on Pr_{1/2}Ca_{1/2}MnO_3, revealing how charge, orbital, and magnetic orders evolve, leading to a transition from an insulating to a metallic ferromagnetic state.

Contribution

First-principles based simulations of ultrafast optical excitation effects on polaronic manganite, capturing charge, orbital, and magnetic order dynamics and transitions.

Findings

Charge/orbital order melts with increasing fluence.

High-fluence induces transition to ferromagnetic metal.

Low-fluence dynamics involve coherent phonons.

Abstract

The dynamics of electrons, spins and phonons induced by optical femtosecond pulses has been simulated for the polaronic crystal $\rm{Pr_{1/2}Ca_{1/2}MnO_3}$. The model used for the simulation has been derived from first-principles calculations. The simulations reproduce the experimentally observed melting of charge/orbital order with increasing fluence. The loss of charge order in the high-fluence regime induces a transition to a ferromagnetic metal. At low fluence, the dynamics is deterministic and coherent phonons are created by the repopulation of electronic orbitals, which are strongly coupled to the phonon degrees of freedom. In contrast to the low-fluence regime, the magnetic transitions occurring at higher fluence can be attributed to a quasi-thermal transition of a cold-plasma-like state with hot electrons and cold phonons and spins. The findings can be rationalized in a more complete picture of the electronic structure that goes beyond the simple ionic picture of charge order.