Mechanical and liquid phase exfoliation of cylindrite: a natural van der Waals superlattice with intrinsic magnetic interactions

Abstract

We report the isolation of thin flakes of cylindrite, a naturally occurring van der Waals superlattice, by means of mechanical and liquid phase exfoliation. We find that this material is a heavily doped p-type semiconductor with a narrow gap (<0.85 eV) with intrinsic magnetic interactions that are preserved even in the exfoliated nanosheets. Due to its environmental stability and high electrical conductivity, cylindrite can be an interesting alternative to the existing two-dimensional magnetic materials.

Nonlinear Optical Response in Natural van der Waals Heterostructures

“…The franckeite is composed of a series of isotropic 2D layers, but it exhibits a spontaneous rippling that makes the material structurally anisotropic. [ 32,33 ] It has been recently shown that the rippling structure of franckeite comes hand in hand with an inhomogeneous in‐plane strain profile and anisotropic electrical, vibrational, and optical properties. [ 34 ] However, there are few reports on the optical response and application of the layered franckeite, especially in the nonlinear optical regime with increasing incident light intensity.…”

Superlattices based on van der Waals 2D materials

“…Elements of the unit cell Modulation by (dimension) Applications (ref. ) Vertical stacking Chemical composition, lattice (mis)match (1D) IR photodetectors 15,16,20 Phase-change memory [28][29][30][31][32][33][34] Thermoelectrics [47][48][49][50] Superconductivity [51][52][53][54] Intercalated compounds Chemical composition, structuring, charge transfer (1D)…”

“…Natural van der Waals superlattices have been obtained by isolating thin layers from minerals such as franckeite [15][16][17][18][19] or cylindrite. 20 Both minerals belong to the family of sulfosalts with the general formula (Pb,Sn) 6+x…”

“…The characterization of the magnetic properties of the thin flakes proved that the intrinsic magnetic interactions present in the bulk mineral are preserved after thinning. 20 Both minerals have the advantage of being stable under ambient conditions. These results underline the existence of more natural minerals from which thin layers with novel properties can be isolated.…”

“…[31][32][33][34] Particularly, the phase change from a Dirac semimetal to a topological insulator as a function of the thickness of the GeTe layer has been observed, which is promising for spintronic applications. 34 In the case of natural minerals such as franckeite 15,16 and cylindrite, 20 it was shown how the alternating formation of layers with dissimilar lattice symmetry gives rise to superlattices that grow with a mismatch, but are ordered and thermodynamically stable. This type of materials, called misfit layer compounds, can be synthesized with controlled properties as well.…”