Ultrafast spin-nematic and ferroelectric phase transitions induced by femto-second light pulses

TL;DR

This study models ultrafast, optically-induced phase transitions in a manganite, revealing how femtosecond light pulses can selectively induce magnetic, spin-nematic, or ferroelectric phases through non-thermal mechanisms.

Contribution

It introduces a first-principles-based model to simulate ultrafast phase transitions in strongly correlated materials driven by light polarization.

Findings

Femtosecond light pulses induce non-thermal magnetic phase transitions.

Light polarization determines whether spin-nematic or ferroelectric phases are excited.

Optically induced ferromagnetic coupling between Mn-trimers drives phase changes.

Abstract

Optically-induced phase transitions of the manganite $\rm Pr_{1/3}Ca_{2/3}MnO_3$ have been simulated using a model Hamiltonian, that captures the dynamics of strongly correlated charge, orbital, lattice, and spin degrees of freedom. Its parameters have been extracted from first-principles calculations. Beyond a critical intensity of a femto-second light pulse, the material undergoes ultra-fast and non-thermal magnetic phase transition from a non-collinear to collinear antiferromagnetic phases. The light-pulse excites selectively either a spin-nematic or a ferroelectric phase depending on the light-polarization. The behavior can be traced to an optically induced ferromagnetic coupling between Mn-trimers, i.e. polarons which are delocalized over three Mn-sites. The polarization guides the polymerization of the polaronic crystal into distinct patterns of ferromagnetic chains determining the target phase.