@article{5602e9e53d564c159f31e28168c6f0c7,
title = "Unexpected Near-Infrared to Visible Nonlinear Optical Properties from 2-D Polar Metals",
abstract = "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 metals (approaching 10 nm/V), are determined by the atomic-level structure and bonding of two-to-three-atom-thick crystalline films. The bond character evolved from covalent to metallic over a few atomic layers, changing the out-of-plane metal-metal bond distances by approximately ten percent (0.2 {\AA}), resulting in symmetry breaking and an axial electrostatic dipole that mediated the large nonlinear response. Two different orientations of the crystalline metal atoms, corresponding to lateral displacements <2 {\AA}, persisted in separate micrometer-scale terraces to generate distinct harmonic polarizations. This strong atomic-level structure-property interplay suggests metal photonic properties can be controlled with atomic precision. ",
author = "Steves, {Megan A.} and Yuanxi Wang and Natalie Briggs and Tian Zhao and Hesham El-Sherif and Bersch, {Brian M.} and Shruti Subramanian and Chengye Dong and Timothy Bowen and {Fuente Duran}, {Ana De La} and Katharina Nisi and Margaux Lassauni{\`e}re and Ursula Wurstbauer and Bassim, {Nabil D.} and Jose Fonseca and Robinson, {Jeremy T.} and Crespi, {Vincent H.} and Joshua Robinson and Knappenberger, {Kenneth L.}",
note = "Funding Information: This research was supported by the Air Force Office of Scientific Research, grant number FA-9550-18-1-0347, and by the National Science Foundation Graduate Research Fellowship Program under grant no. DGE1255832. This work was also supported by the National Science Foundation, award number CHE-1807999 and under NSF DMR-2011839 through the Penn State MRSEC–Center for Nanoscale Science. Funding for this work was also provided by the Northrop Grumman Mission Systems{\textquoteright} University Research Program, Semiconductor Research Corporation Intel/Global Research Collaboration Fellowship Program, task 2741.001, the National Science Foundation (NSF) CAREER Awards 1453924 and 1847811, the Chinese Scholarship Council, an Alfred P. Sloan Research Fellowship, the NSF DMR-1708972, DMR-1420620, and 1808900, and the 2D Crystal Consortium NSF Materials Innovation Platform under cooperative agreement DMR-1539916. Funding for the McMaster work was by AFOSR award FA9550-19-1-0239 and the NSERC Natural Sciences and Engineering Research Council of Canada Discovery Grant program. All electron microscopy was performed at the Canadian Centre for Electron Microscopy. The work at NRL was funded through the Office of Naval Research. Funding Information: This research was supported by the Air Force Office of Scientific Research, grant number FA-9550-18-1-0347, and by the National Science Foundation Graduate Research Fellowship Program under grant no. DGE1255832. This work was also supported by the National Science Foundation, award number CHE-1807999 and under NSF DMR-2011839 through the Penn State MRSEC?Center for Nanoscale Science. Funding for this work was also provided by the Northrop Grumman Mission Systems? University Research Program, Semiconductor Research Corporation Intel/Global Research Collaboration Fellowship Program task 2741.001, the National Science Foundation (NSF) CAREER Awards 1453924 and 1847811, the Chinese Scholarship Council, an Alfred P. Sloan Research Fellowship, the NSF DMR-1708972, DMR-1420620, and 1808900 and the 2D Crystal Consortium NSF Materials Innovation Platform under cooperative agreement DMR-1539916. Funding for the McMaster work was by AFOSR award FA9550-19-1-0239 and the NSERC Natural Sciences and Engineering Research Council of Canada Discovery Grant program. All electron microscopy was performed at the Canadian Centre for Electron Microscopy. The work at NRL was funded through the Office of Naval Research. Publisher Copyright: {\textcopyright} 2020 American Chemical Society. All rights reserved.",
year = "2020",
month = nov,
day = "11",
doi = "10.1021/acs.nanolett.0c03481",
language = "English (US)",
volume = "20",
pages = "8312--8318",
journal = "Nano Letters",
issn = "1530-6984",
publisher = "American Chemical Society",
number = "11",
}