Symmetry Breakdown in Franckeite: Spontaneous Strain, Rippling, and Interlayer Moiré

• Published in: Nano letters Vol. 20; no. 2; pp. 1141 - 1147
• Main Authors: Frisenda, Riccardo, Sanchez-Santolino, Gabriel, Papadopoulos, Nikos, Urban, Joanna, Baranowski, Michal, Surrente, Alessandro, Maude, Duncan K, Garcia-Hernandez, Mar, van der Zant, Herre S. J, Plochocka, Paulina, San-Jose, Pablo, Castellanos-Gomez, Andres
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12-02-2020
• Subjects: strain; interlayer moiré; franckeite; 2D material; anisotropic material; interlayer moiré
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.9b04536

Franckeite is a naturally occurring layered mineral with a structure composed of alternating stacks of SnS2-like and PbS-like layers. Although this superlattice is composed of a sequence of isotropic two-dimensional layers, it exhibits a spontaneous rippling that makes the material structurally anisotropic. We demonstrate that this rippling comes hand in hand with an inhomogeneous in-plane strain profile and anisotropic electrical, vibrational, and optical properties. We argue that this symmetry breakdown results from a spatial modulation of the van der Waals interaction between layers due to the SnS2-like and PbS-like lattices incommensurability.