Naturally Occurring 2D Heterostructure Nagyágite with Anisotropic Optical Properties

Abstract

a wide range of applications under the umbrella of one single material. [9][10][11][12][13][14] In addition to the focused direction of the artificial stacking of 2D material layers to fabricate heterostructures, the exfoliation of natural layered minerals consisting of alternating material building blocks has also come into the foray as an efficient way of creating ultrathin vdW heterostructures. Recently, it has been demonstrated that natural vdW minerals such as franckeite [15][16][17] and cylindrite [18] composed of alternating PbS-and SnS 2 -like layers can be exfoliated to a few layer thicknesses for realizing diverse optoelectronic and optical applications such as photodetection, linear dichroism, nonlinear harmonic generation, [19] and large Kerr nonlinearity. [20]

Natural 2D layered mineral cannizzarite with anisotropic optical responses

“…Previously, angle-resolved polarized Raman spectroscopy has been employed to determine the structural anisotropy in monoclinic 2D crystals such as MoTe 2 57 and GeAs 18 . Moreover, the technique has also been used for probing the structural anisotropy in other natural vdW heterostructures such as cylindrite 32 , franckeite 36 , 37 , lengenbachite 35 , and nagyágite 58 . The contour color map in Fig.…”

“…Here, corresponds to the incident linear polarization being along the -direction. Therefore, the angle-dependent Raman intensities of the parallel polarization components of the A g and B g modes can be written as 58 , where is the phase difference between and . From Eq.…”

Polarization-sensitive optical responses from natural layered hydrated sodium sulfosalt gerstleyite

“…From literature, the real part of the refractive index of gerstleyite crystal is around 2.01 58 . Thus, considering all the experimental parameters into account, the third-order nonlinear susceptibility magnitude of for gerstleyite crystal is estimated as 1.81 × 10 –20 m 2 /V 2 , which has the same order of magnitude as the recently explored multi-element anisotropic nonlinear vdW layered materials for example franckeite (1.87 × 10 –19 m 2 /V 2 ) 26 , cylindrite (3.06 × 10 –19 m 2 /V 2 ) 27 , teallite (3.49 × 10 –19 m 2 /V 2 ) 29 , gillulyite (2.05 × 10 –20 m 2 /V 2 ) 30 , getchellite (2.89 × 10 –20 m 2 /V 2 ) 18 , and nagyágite (1.49 × 10 –20 m 2 /V 2 ) 59 .…”

Large in-plane vibrational and optical anisotropy in natural 2D heterostructure abramovite

“…Hence, angle-resolved polarized Raman spectroscopy studies can unveil the in-plane structural anisotropy in the triclinic crystal of abramovite by analyzing the anisotropic phonon vibrational modes. This method has previously been used for determining the crystal anisotropy in other sulfosalt minerals such as cylindrite 28 , frankeite 40 , lengenbachite 31 , cannizzarite 32 , and nagyágite 55 . Figure 3 b shows the contour color map of the variation of Raman intensity for the parallel polarization components of the Raman modes within the range of 65 to 600 cm -1 as a function of the incident linear polarization angle , where for the polarization along the x -axis as labeled in Fig.…”

“…Structural anisotropy in a vdW heterostructure induces linear dichroism. Previously, polarization-dependent absorption measurements have been used to probe the linear dichroism and the crystal axes of other natural anisotropic vdW heterostructures such as cylindrite 28 , franckeite 40 , lengenbachite 31 , cannizzarite 32 , and nagyágite 55 . With that hindsight, next we investigate the evolution of the absorbance in abramovite crystal depending on the incident light polarization for the same 26 nm-thick flake.…”