Unexpected Near-Infrared to Visible Nonlinear Optical Properties from 2-D Polar Metals

• DOI: 10.1021/acs.nanolett.0c03481
• Publication Date: 2020-10-20T18:51:23Z
• Authors: Megan A. Steves; Yuanxi Wang; Natalie Briggs; Tian Zhao; Hesham El-Sherif; Brian M. Bersch; Shruti Subramanian; Chengye Dong; Timothy Bowen; Ana De La Fuente ...; Katharina Nisi; Margaux Lassaunière; Ursula Wurstbauer; Nabil D. Bassim; Jose Fonseca; Jeremy T. Robinson; Vincent H. Crespi; Joshua Robinson; Kenneth L. Knappe...
• Keywords: 02 engineering and technology; 0210 nano-technology

Near-infrared-to-visible second harmonic generation from air-stable two-dimensional polar gallium and indium metals is described. The photonic properties of 2D metals, including the largest second-order susceptibilities reported for (approaching 10 nm/V), are determined by atomic-level structure bonding two-to-three-atom-thick crystalline films. bond character evolved covalent to metallic over a few atomic layers, changing out-of-plane metal–metal distances approximately ten percent (0.2 Å), resulting in symmetry breaking an axial electrostatic dipole that mediated large nonlinear response. Two different orientations metal atoms, corresponding lateral displacements <2 Å, persisted separate micrometer-scale terraces generate distinct polarizations. This strong structure–property interplay suggests can be controlled with precision.