Quenched lattice fluctuations in optically driven SrTiO₃.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Crystal lattice fluctuations influence equilibrium phase transitions in quantum materials.
• Their role in light-induced phase transitions is under-explored.
• Strontium titanate (SrTiO3) exhibits competing polar instabilities and antiferrodistortive rotations, hindering ferroelectricity.

Purpose of the Study:

• Investigate the dynamics of lattice fluctuations during light-induced phase changes.
• Understand the influence of lattice dynamics on ferroelectric phase transitions in SrTiO3.
• Explore the competition between different instabilities under external stimuli.

Main Methods:

• Utilized high-intensity mid-infrared optical pulses to excite the Ti-O-stretching mode (17 THz) in SrTiO3.
• Employed time-resolved X-ray diffuse scattering at a free-electron laser to measure lattice fluctuations.
• Applied theoretical models incorporating nonlinear phononic interactions and strain coupling.

Main Results:

• Observed a rapid increase followed by a long-lived decrease (quench) in R-point antiferrodistortive lattice fluctuations.
• Demonstrated that lattice fluctuations can be dynamically controlled by external light fields.
• Theoretically explained the observed quench through nonlinear phononic interactions and strain coupling.

Conclusions:

• Light-induced changes in lattice fluctuations are crucial for understanding ferroelectric phase transitions.
• The study provides a framework for controlling quantum material properties with light.
• Offers testable hypotheses for the underlying physics of light-induced ferroelectricity in quantum materials.