Implementation of a laser-neutron pump-probe capability for inelastic neutron scattering

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Understanding nonequilibrium dynamics in spin systems is crucial for fundamental science and technological advancements.
• Inelastic neutron scattering (INS) is vital for studying spin excitations but traditionally limited to equilibrium measurements.
• The re-equilibration dynamics of spin excitations remain largely unknown with conventional methods.

Purpose of the Study:

• To design and implement a time-resolved laser-neutron pump-probe capability for studying nonequilibrium spin dynamics.
• To enable the excitation of out-of-equilibrium magnons and probe their behavior using INS.
• To open new research avenues for investigating dynamic phenomena in quantum materials.

Main Methods:

• Developed a time-resolved laser-neutron pump-probe setup at the Spallation Neutron Source (SNS) hybrid spectrometer.
• Utilized a nanosecond pulsed laser to excite nonequilibrium magnons.
• Employed inelastic neutron scattering (INS) for probing laser-induced dynamics with time synchronization.

Main Results:

• Successfully implemented a novel laser-neutron pump-probe capability for dynamic studies.
• Demonstrated the resolution of laser-induced nonequilibrium structure factors in a quantum magnet via INS.
• Established a method for time-resolved measurements of spin excitation re-equilibration.

Conclusions:

• The developed technique provides advanced capabilities for out-of-equilibrium measurements at SNS.
• This method allows direct observation of nonequilibrium spin dynamics, previously inaccessible.
• Paves the way for exploring novel out-of-equilibrium phenomena in magnetic materials using neutron scattering.