Floquet optical selection rules in black phosphorus

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Spectroscopy

Background:

• Symmetry-endorsed optical selection rules are vital for understanding quantum material optical properties and ultrafast spectral dynamics.
• Existing frameworks struggle to fully elucidate complex pump-probe photoemission spectra in materials like black phosphorus.

Purpose of the Study:

• To introduce and apply momentum-resolved Floquet optical selection rules for analyzing pump-probe photoemission spectra in monolayer black phosphorus (BP).
• To elucidate the influence of material and laser symmetries on spectral distributions.
• To provide a theoretical framework for understanding light-induced ultrafast phenomena in Floquet systems.

Main Methods:

• Utilized group theory to develop momentum-resolved Floquet optical selection rules.
• Employed time-dependent density functional theory (TDDFT) to investigate the dynamical evolution of Floquet(-Volkov) states.
• Analyzed spectral weight distributions at specific momenta for each sideband in photoemission spectra.

Main Results:

• Successfully elucidated pump-probe photoemission spectral distributions of monolayer BP using the proposed Floquet optical selection rules.
• Revealed spectral weights of Floquet(-Volkov) states at specific momenta, comprehensively explained by the new selection rules.
• Demonstrated the framework's ability to clarify experimental spectra and uncover unexplored characteristics under varying pump-probe configurations.

Conclusions:

• The developed momentum-resolved Floquet optical selection rules provide a robust explanation for ultrafast spectral phenomena in monolayer BP.
• This framework deepens the understanding of light-induced ultrafast spectra in BP and offers potential for application to other Floquet systems.
• The study highlights the critical role of combined material and laser symmetries in dictating optical properties.