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arXiv 2112.04853cond-mat.mtrl-sci
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二维SnS中面内各向异性的非线性光学成像

Nonlinear optical imaging of in-plane anisotropy in two-dimensional SnS

G. M. Maragkakis, S. Psilodimitrakopoulos, L. Mouchliadis, A. S. Sarkar, A. Lemonis, G. Kioseoglou, E. Stratakis

摘要:

二维硫化锡(SnS)晶体是一类正交晶系半导体材料,具有面内各向异性、多铁性和不对称性等优异的光学和电学特性,近年来引起了人们的广泛兴趣。二维SnS晶体沿平面扶手椅(AC)和锯齿形(ZZ)晶体方向表现出各向异性响应,提供了额外的自由度来操纵它们的行为。因此,计算AC/ZZ方向在表征2D SnS晶体中是重要的。在这项工作中,我们利用二维SnS晶体,产生二次谐波产生(SHG)的反转对称性的缺乏,进行偏振分辨SHG(P-SHG)的面内各向异性的非线性成像。我们用非线性光学模型拟合了P-SHG实验数据,这使我们能够从2D晶体的每个点计算AC/ZZ取向,并以高分辨率映射属于同一视场的几个2D SnS薄片的AC/ZZ方向。研究发现,P-SHG强度极坐标图与薄片的晶轴以及不同方向上二阶非线性极化率张量的相对强度有关。因此,我们的方法提供了正交二维晶体的光学面内各向异性的定量信息,在新兴的光电应用中,这种晶体的器件操作过程中的性能表征提供了很大的希望。

英文摘要:

Two-dimensional (2D) tin(II) sulfide (SnS) crystals belong to a class of orthorhombic semiconducting materials that are lately attracting significant interest, given their remarkable properties, such as in-plane anisotropic optical and electronic response, multiferroic nature and lack of inversion symmetry. The 2D SnS crystals exhibit anisotropic response along the in-plane armchair (AC) and zigzag (ZZ) crystallographic directions, offering an additional degree of freedom in manipulating their behavior. Therefore, calculating the AC/ZZ directions is important in characterizing the 2D SnS crystals. In this work, we take advantage of the lack of inversion symmetry of the 2D SnS crystal, that produces second harmonic generation (SHG), to perform polarization-resolved SHG (P-SHG) nonlinear imaging of the in-plane anisotropy. We fit the P-SHG experimental data with a nonlinear optics model, that allows us to calculate the AC/ZZ orientation from every point of the 2D crystal and to map with high-resolution the AC/ZZ direction of several 2D SnS flakes belonging in the same field of view. It is found that the P-SHG intensity polar patterns are associated with the crystallographic axes of the flakes and with the relative strength of the second order nonlinear susceptibility tensor in different directions. Therefore, our method provides quantitative information of the optical in-plane anisotropy of orthorhombic 2D crystals, offering great promise for performance characterization during device operation in the emerging optoelectronic applications of such crystals.

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