Tracking the anisotropic electron dynamics in SnSe by time- and polarization-resolved high-harmonic spectroscopy

Area of Science:

• Condensed matter physics
• Materials science
• Ultrafast spectroscopy

Background:

• Tin selenide (SnSe) exhibits anisotropic electronic properties, offering unique possibilities for studying directional carrier dynamics.
• Conventional spectroscopy methods struggle to resolve these polarization-dependent effects in anisotropic materials.

Purpose of the Study:

• To investigate anisotropic ultrafast carrier dynamics in SnSe thin films.
• To demonstrate the capability of time-resolved high-harmonic spectroscopy (TR-HHS) for probing directional electronic processes.

Main Methods:

• Utilized time-resolved high-harmonic spectroscopy (TR-HHS) to study SnSe thin films.
• Analyzed the evolution of the TR-HHS signal over femtosecond to picosecond timescales.
• Examined the dependence of the signal on crystal orientation.

Main Results:

• Observed strong crystal orientation dependence in the TR-HHS signal.
• The signal evolution occurred over hundred-femtosecond to few-picosecond timescales.
• Attributed the observed dynamics to anisotropic electronic relaxation, including electron thermalization and phonon-mediated hot-electron cooling.

Conclusions:

• TR-HHS is a powerful all-optical method for studying symmetry-governed electron dynamics in anisotropic materials.
• The findings provide strategies for developing novel polarization-tunable optoelectronic devices based on anisotropic materials like SnSe.