Correlating Quasi-Electron Relaxation with Quantum Femtosecond Magnetism in the Order Parameter Dynamics of Insulating Manganites

TL;DR

This study reveals how femtosecond laser pulses induce a rapid antiferro-to-ferromagnetic transition in manganites by correlating quasi-electron relaxation with quantum femtosecond magnetism, highlighting a transient coupling of spin, charge, and lattice.

Contribution

It provides new insights into the ultrafast dynamics of charge and spin in manganites, demonstrating the coexistence of different quasi-particles and their role in magnetic phase transitions.

Findings

Reversal of quasi-particle populations above a threshold intensity

Coexistence of fast metallic and slow polaronic carriers

Laser-driven charge reorganization linked to quantum femtosecond magnetism

Abstract

Femtosecond (fs)-resolved simultaneous measurements of charge and spin dynamics reveal the coexistence of two different quasi-particle excitations in colossal magneto-resistive (CMR) manganites, with {\em fs} and {\em ps} relaxation times respectively. Their populations reverse size above a {\em photoexcitation-intensity-threshold} coinciding with a "sudden" antiferro-to-ferromagnetic switching during $<$100 fs laser pulses. We present evidence that fast, metallic, mobile quasi--electrons dressed by {\em quantum spin fluctuations} coexist with slow, localized, polaronic charge carriers in non-equilibrium phases. This may be central to CMR transition and leads to a laser-driven charge reorganization simultaneously with quantum fs magnetism via an emergent quantum-spin/charge/lattice transient coupling.