Strong second harmonic generation in two-dimensional ferroelectric IV-monochalcogenides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Two-dimensional (2D) ferroelectrics are materials with spontaneous electric polarization.
• GeS, GeSe, SnS, and SnSe are 2D materials with potential for unique electronic and optical properties.
• Enhanced shift-current response is desirable for non-linear optical applications.

Purpose of the Study:

• To investigate the second harmonic generation (SHG) properties of 2D ferroelectrics GeS, GeSe, SnS, and SnSe.
• To compare the SHG response of these materials with existing benchmarks like GaAs.
• To understand the relationship between shift-current response and SHG in these materials.

Main Methods:

• Density functional theory (DFT) calculations were employed to model the electronic and optical properties.
• A one-dimensional two-band model was used to analyze the optical response along the polarization direction.
• Effective second harmonic generation coefficients were calculated.

Main Results:

• GeS, GeSe, SnS, and SnSe exhibit the largest effective second harmonic generation (SHG) reported to date.
• The SHG magnitudes can reach up to [Formula: see text], an order of magnitude greater than GaAs.
• A direct proportionality was found between the shift-current response and the SHG tensor within the model.

Conclusions:

• The investigated 2D ferroelectrics possess exceptional SHG properties.
• Their large shift-current and SHG responses make them highly promising for non-linear optical and optoelectronic applications.
• These materials offer a new avenue for developing advanced photonic devices.