Antiphase Oscillations in the Time-Resolved Spin Structure Factor of a Photoexcited Mott Insulator

TL;DR

This study uses numerical simulations to explore how the spin structure factor in a photoexcited Mott insulator exhibits antiphase oscillations, revealing phase differences linked to two-magnon excitations, with implications for future experimental observations.

Contribution

It uncovers the antiphase oscillation behavior in the spin structure factor and connects it to the $B_{1g}$ two-magnon excitation channel, advancing understanding of spin dynamics in photoexcited Mott insulators.

Findings

Oscillations in spin structure factor depend on momentum and are antiphase between orthogonal directions.

The phase difference originates from the $B_{1g}$ two-magnon excitation channel.

Observation of these oscillations poses experimental challenges for TRRIXS with current resolution.

Abstract

Motivated by the recent development of time-resolved resonant-inelastic x-ray scattering (TRRIXS) in photoexcited antiferromagnetic Mott insulators, we numerically investigate momentum-dependent transient spin dynamics in a half-filled Hubbard model on a square lattice. After turning off a pumping photon pulse, the intensity of a dynamical spin structure factor temporally oscillates with frequencies determined by the energy of two magnons in the antiferromagnetic Mott insulator. We find an antiphase behavior in the oscillations between two orthogonal momentum directions, parallel and perpendicular to the electric field of a pump pulse. The phase difference comes from the $B_{1g}$ channel of the two-magnon excitation. Observing the antiphase oscillations will be a big challenge for TRRIXS experiments when their time resolution will be improved by more than an order of magnitude.