Nonthermal breaking of magnetic order via photogenerated spin defects in the spin-orbit coupled insulator Sr3Ir2O7

Abstract

In many strongly correlated insulators, antiferromagnetic order competes with exotic and technologically relevant phases, like superconductivity. While control of spin order is critical to stabilize different functional states, elucidating the mechanism of laser-induced demagnetization in complex oxides remains a challenge. It is unknown if the optical pulse can quench magnetization nonthermally or if it instead only acts as a heat source. Here, we use ultrafast, broadband, optical spectroscopy to track the responses of the electronic, lattice, and spin degrees of freedom and their relation to antiferromagnetism in the strongly spin-orbit coupled insulator Sr 3 Ir 2 O 7 . We find that magnetization can be rapidly and strongly suppressed on a sub-150 fs timescale. At low excitation fluences, the magnetic recovery is fast; however, the recovery time increases dramatically with the magnitude of demagnetization. At the same time, we show that the lattice, evidenced through the A g phonon frequencies, appears to remain below T N , suggesting that the system remains nonthermal during the optical modulation of spin order. We suggest that photogenerated spin defects are responsible for the long-lived demagnetized state and discuss its implications for optical control of solids.

Ultrafast Loss of Lattice Coherence in the Light-Induced Structural Phase Transition of V2O3

“…2), either pumping with short (15 fs), 700 nm laser pulses and probing in the IR with a short (15 fs) 1800 nm pulse at 1 kHz repetition rate (red traces), or pumping with a 30 fs, 800 nm pulse and probing in the visible with frequency-resolved white-light supercontinuum (Fourier transform limit 15 fs, 500-750 nm) at 5 kHz repetition rate (blue traces). The use of multiple probes allows us to achieve greater sensitivity to the phonon modes, as each mode may modulate a different spectral region [19][20][21].…”