Non-thermal breaking of magnetic order via photo-generated spin defects

TL;DR

This study demonstrates that ultrafast optical pulses can non-thermally disrupt and stabilize a long-lived demagnetized state in a Mott insulator through photo-generated spin defects, revealing new transient magnetic phases.

Contribution

It introduces a mechanism where photo-induced spin defects stabilize a demagnetized state without heating the lattice, advancing understanding of ultrafast magnetic control.

Findings

Light can non-thermally melt long-range spin order.

Magnetic order recovers within 1 ps at low fluences.

High fluences induce a long-lived demagnetized state.

Abstract

In Mott insulators the evolution of antiferromagnetic order to superconducting or charge-density-wave-like states upon chemical doping underpins the control of quantum phases. Photo-doping can induce similar transitions on the ultrafast timescale, however the response of the spin system has remained elusive. Here, we use 4D-ultrafast optical spectroscopy to extract quantitative magnetic dynamics in the spin-orbit coupled Mott insulator Sr3Ir2O7. We demonstrate that light can non-thermally melt long-range spin order. At low fluences magnetic order recovers within 1 ps despite demagnetization of roughly 50%. However, high fluences induce a crossover to a long-lived demagnetized state without increasing the lattice temperature. We show that the generation of photo-induced spin defects enables a mechanism that stabilizes the demagnetized state which could help expose new transient phases.