Thermally-driven phase transitions in freestanding low-buckled silicene, germanene, and stanene

Abstract

Low-buckled silicene, germanene, and stanene are group$-IV$ graphene allotropes. They form a honeycomb lattice out of two interpenetrating ($A$ and $B$) triangular sublattices that are vertically separated by a small distance ${\Delta }_z$. The atomic numbers $Z$ of silicon, germanium, and tin are larger to carbon's ($Z_C=6$), making them the first experimentally viable two-dimensional topological insulators. Those materials have a twice-energy-degenerate atomistic structure characterized by the buckling direction of the $B$ sublattice with respect to the $A$ sublattice [whereby the $B-$atom either protrudes {\em above} (${\Delta }_z>0$) or {\em below} (${\Delta }_z<0$) the $A-$atoms], and the consequences of that energy degeneracy on their elastic and electronic properties have not been reported thus far. Here, we uncover {\em ferroelastic, bistable} behavior on silicene, which turns into an {\em average} planar structure at about 600 K. Further, the creation of electron and hole puddles obfuscates the zero-temperature SOC induced band gaps at temperatures as low as 200 K, which may discard silicene as a viable two-dimensional topological insulator for room temperature applications. Germanene, on the other hand, never undergoes a low-buckled to planar 2D transformation, becoming amorphous at around 675 K instead, and preserving its SOC-induced bandgap despite of band broadening. Stanene undergoes a transition onto a crystalline 3D structure at about 300 K, preserving its SOC-induced electronic band gap up to that temperature. Unlike what is observed in silicene and germanene, stanene readily develops a higher-coordinated structure with a high degree of structural order. The structural phenomena is shown to have deep-reaching consequences for the electronic and vibrational properties of those two dimensional topological insulators.

arXiv comment16 pages, 21 figures. Originally submitted on December 5, 2022

References in corpus (29)

• The SIESTA method for ab initio order-N materials simulation
• Efficient index handling of multidimensional periodic boundary conditions
• Quantum Spin Hall Effect in Graphene
• Two and one-dimensional honeycomb structures of silicon and germanium
• Epitaxial Growth of Two-Dimensional Stanene
• Germanene: a novel two-dimensional Germanium allotrope akin to Graphene and Silicene
• Observation of Electron-Hole Puddles in Graphene Using a Scanning Single Electron Transistor
• Epitaxial Growth of a Silicene Sheet
• Large-gap quantum spin Hall insulators in tin films
• Nonlocal magnetization dynamics in ferromagnetic heterostructures
• Spin-orbit coupling in curved graphene, fullerenes, nanotubes, and nanotube caps
• Group-IV graphene- and graphane-like nanosheets
• Multiferroic Two-Dimensional Materials
• Colloquium: Physical properties of group-IV monochalcogenide monolayers
• Electron-hole puddles in the absence of charged impurities
• Structural phase transition and material properties of few-layer monochalcogenides
• Two-dimensional disorder in black phosphorus and monochalcogenide monolayers
• Stability and properties of high-buckled two-dimensional tin and lead
• Tuning the ferro- to para-electric transition temperature and dipole orientation of group-IV monochalcogenide monolayers
• Strain gauge fields for rippled graphene membranes under central mechanical load: an approach beyond first-order continuum elasticity
• Graphene's morphology and electronic properties from discrete differential geometry
• Strain-engineering of graphene's electronic structure beyond continuum elasticity
• Thermoelectricity of Tin Selenide Monolayers Across a Structural Phase Transition
• Group-IV monochalcogenide monolayers: two-dimensional ferroelectrics with weak intra-layer bonds and a phosphorene-like monolayer dissociation energy
• Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials
• Slippery paraelectric transition metal dichalcogenide bilayers
• Quantum paraelastic two-dimensional materials
• Evolution of elastic moduli through a two-dimensional structural transformation
• Elasticity of 2D ferroelectrics across their paraelectric phase transformation