First-principles prediction of ferroelectric Janus Si2XY (X/Y = S/Se/Te, X ≠ Y) monolayers with negative Poisson's ratios

The discovery of novel ferroelectric Janus Si 2 XY (X/Y = S/Se/Te, X ≠ Y) monolayers with negative Poisson's ratios presents exciting prospects for various applications in nanomechanical, nanoelectronic and optoelectronic devices.