Raman tensor of layered black phosphorus

Abstract

Abstract Black phosphorus has a strong Raman anisotropy on the basal and cross planes due to its orthorhombic crystal structure. However, almost all the studies on black phosphorus’ anisotropy focus on basal plane with the cross plane neglected. Here, we performed a systematic angle-resolved polarized Raman scattering on both the basal and cross planes of black phosphorus and obtained its integral Raman tensors. It is discovered that when the polarization direction of excitation light is along different crystal axes, the Raman intensity ratio ( I xx : I yy : I zz ) of $$ {A}_g^1 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mi>g</mml:mi> <mml:mn>1</mml:mn> </mml:msubsup> </mml:math> mode is 256:1:5. Besides, via calculation, it is confirmed that the strong Raman anisotropy mainly comes from different differential polarizability alone different directions. This phenomenon is also observed when it comes to the $$ {A}_g^2 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mi>g</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> mode.