Naturally occurring layered mineral franckeite with anisotropic Raman scattering and third-harmonic generation responses

Abstract

Vertically stacked van der Waals (vdW) heterostructures have introduced a unique way to engineer optical and electronic responses in multifunctional photonic and quantum devices. However, the technical challenges associated with the artificially fabricated vertical heterostructures have emerged as a bottleneck to restrict their proficient utilization, which emphasizes the necessity of exploring naturally occurring vdW heterostructures. As one type of naturally occurring vdW heterostructures, franckeite has recently attracted significant interest in optoelectronic applications, but the understanding of light–matter interactions in such layered mineral is still very limited especially in the nonlinear optical regime. Herein, the anisotropic Raman scattering and third-harmonic generation (THG) from mechanically exfoliated franckeite thin flakes are investigated. The observed highly anisotropic Raman modes and THG emission patterns originate from the low-symmetry crystal structure of franckeite induced by the lattice incommensurability between two constituent stacked layers. The thickness-dependent anisotropic THG response is further analyzed to retrieve the third-order nonlinear susceptibility for franckeite crystal. The results discussed herein not only provide new insights in engineering the nonlinear light–matter interactions in natural vdW heterostructures, but also develop a testbed for designing future miniaturized quantum photonics devices and circuits based on such heterostructures.

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 .…”

“…Recently, complex multi-element vdW layered materials have attracted vast attention in the context of anisotropic linear and nonlinear optical responses 18 , 26 – 30 . Since the anisotropic optical responses are prominently material specific, it is obligatory to explore more new types of multi-element vdW materials for thriving their unique physical properties and increased adaptability and versatility in more applications.…”

Anisotropic optical responses of layered thallium arsenic sulfosalt gillulyite

“…All the A g modes show anisotropic two-lobe patterns with the Raman intensity maxima either at 0° and 180° or 90° and 270°. Moreover, the orientation of A g modes in parallel polarization configuration indicates the crystal axis of the investigated gillulyite flake 13 , 36 . Here, the 0° and 90° directions are acknowledged as the a -axis (along x -axis) and b -axis (along y -axis) of gillulyite crystal, for further analyzing the anisotropic linear and nonlinear optical properties of the crystal.…”

“…Moreover, the induction of novel complex nanomaterials would also allow the increased adaptability and versatility of the 2D materials world. In recent years, multi-element 2D materials 5 , 9 , 12 , 13 with their unconventional physical properties such as linear dichroism transition 14 , exceptional charge carrier mobility 15 , 16 , favorable band structure 17 , and bandgap transition have gained significant attention in the context of ultrafast photonics applications 18 , 19 . However, research on complex multi-element 2D materials is still in the nascent phase, and the fundamental understanding of their structural and electronic properties and other microscopic processes which affect the linear and nonlinear optical responses in these materials is very limited.…”

Polarization-dependent optical responses in natural 2D layered mineral teallite

“…As an alternate, naturally occurring layered minerals pave an interesting way to prepare multi-element ultrathin flakes via mechanical exfoliation 25 , 26 . In recent years, variety of natural vdW minerals such as teallite 27 , franckeite 28 , 29 and getchellite 30 have been explored. Among these, as one type of naturally occurring vdW sulfosalt mineral, teallite has recently attained significant interest for advanced optoelectronic applications 27 , 31 , 32 .…”