Distinct Charge and Spin Recovery Dynamics in a Photoexcited Mott Insulator

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Spin-orbit coupled Mott insulators like strontium iridate (Sr_{2}IrO_{4}) exhibit complex electronic and magnetic behaviors.
• Understanding non-equilibrium dynamics in these correlated systems is crucial for uncovering fundamental physics and potential applications.

Purpose of the Study:

• To investigate the pump-probe response of the Mott insulator Sr_{2}IrO_{4} under laser excitation.
• To elucidate the distinct timescales governing charge dynamics and magnetic order recovery.
• To explore the fundamental origins of these dynamics in correlated electron systems.

Main Methods:

• Experimental pump-probe spectroscopy to observe changes in optical weight and magnetic order.
• Theoretical modeling combining spatiotemporal mean-field dynamics and Langevin dynamics.
• Simulations on a photoexcited Mott-Hubbard insulator model in two dimensions.

Main Results:

• Laser pumping rapidly suppresses three-dimensional magnetic order and creates low-energy optical weight.
• Post-pump, optical weight reduces quickly, while magnetic order recovery is significantly slower.
• The timescale difference is intrinsic to charge dynamics versus order reconstruction, not a dimensional effect, with magnetic recovery time increasing with pump fluence.

Conclusions:

• The observed timescale difference in Sr_{2}IrO_{4} is an intrinsic property of correlated systems, related to charge dynamics and order reconstruction.
• The theoretical framework provides insights into phase competition and spatial ordering in various quantum materials out of equilibrium.
• This work offers a new approach to analyze non-equilibrium phenomena in superconductors and charge-ordered systems.