Photogalvanic effect in monolayer black phosphorus.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Physics

Background:

• Monolayer black phosphorus (MBP) possesses unique electronic properties.
• Photogalvanic effects (PGEs) are crucial for optoelectronic applications.
• Understanding symmetry-induced phenomena in 2D materials is key.

Purpose of the Study:

• To develop a first-principles theoretical approach for analyzing linear and circular photogalvanic effects (PGEs).
• To investigate PGE phenomena in sulfur-doped monolayer black phosphorus (MBP).
• To explore the impact of impurity doping on symmetry and photoresponse.

Main Methods:

• Density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism.
• First-principles calculations to analyze electronic band structure and optical transitions.
• Symmetry analysis of the doped MBP lattice.

Main Results:

• Impurity doping of MBP breaks space inversion symmetry, resulting in C s symmetry.
• Linear PGE is induced in both zigzag and armchair directions; circular PGE is induced along the zigzag direction.
• A robust broadband photoresponse from near-infrared to visible light is predicted.
• Significant anisotropy in PGE is observed, with zigzag direction response being an order of magnitude larger.
• PGE originates from inter-band transitions involving impurity and valence bands to conduction bands.

Conclusions:

• The theoretical approach accurately predicts PGE phenomena in doped 2D materials.
• Sulfur doping in MBP creates a material with tunable and anisotropic photoresponse.
• The findings offer insights for designing novel photodetectors and optoelectronic devices based on 2D materials.