Strong second harmonic generation in two-dimensional ferroelectric IV-monochalcogenides

Abstract

The two-dimensional ferroelectrics GeS, GeSe, SnS and SnSe are expected to have large spontaneous in-plane electric polarization and enhanced shift-current response. Using density functional methods, we show that these materials also exhibit the largest effective second harmonic generation reported so far. It can reach magnitudes up to $10$ nm/V which is about an order of magnitude larger than that of prototypical GaAs. To rationalize this result we model the optical response with a simple one-dimensional two-band model along the spontaneous polarization direction. Within this model the second-harmonic generation tensor is proportional to the shift-current response tensor. The large shift current and second harmonic responses of GeS, GeSe, SnS and SnSe make them promising non-linear materials for optoelectronic applications.

4 pages 3 figures, typos fixed, updated references, published version

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• Experimental formation of monolayer group-IV monochalcogenides
• Topology of atomically thin soft ferroelectric membranes at finite temperature
• Strong bulk photovoltaic effect and second-harmonic generation in two-dimensional selenium and tellurium
• Thermoelectricity of Tin Selenide Monolayers Across a Structural Phase Transition
• Review of Nanolayered Post-transition Metal Monochalcogenides: Synthesis, Properties, and Applications
• Group-IV monochalcogenide monolayers: two-dimensional ferroelectrics with weak intra-layer bonds and a phosphorene-like monolayer dissociation energy
• Evolution of elastic moduli through a two-dimensional structural transformation
• Optoelectronic characterisation of twisted germanium sulfide nanowires with experimental observation of intrinsic ferroelectricity
• Quantum-Geometric Origin of Out-of-plane Stacking Ferroelectricity
• Significant Second-Harmonic Generation and Bulk Photovoltaic Effect in Trigonal Selenium and Tellurium Chains