Diffusional phase-change materials, such as Ge-Sb-Te alloys, are used in rewritable nonvolatile memory devices. But the continuous pursuit of readout/write speed and reduced energy consumption in miniaturized devices calls for an optically driven, diffusionless phase change scheme in ultrathin materials. Inspired by optical tweezers, in this work, we illustrate theoretically and computationally that a linearly polarized laser pulse with selected frequency can drive an ultrafast diffusionless martensitic phase transition of two-dimensional ferroelastic materials such as SnO and SnSe monolayers, where the unit-cell strain is tweezed as a generalized coordinate that affects the anisotropic dielectric function and electromagnetic energy density. At laser power of 2.0 × 1010 and 7.7 × 109 W/cm2, the transition potential energy barrier vanishes between two 90°-orientation variants of ferroelastic SnO and SnSe monolayer, respectively, so displacive domain switching can occur within picoseconds. The estimated adiabatic thermal limit of energy input in such optomechanical martensitic transition (OMT) is at least 2 orders of magnitude lower than that in Ge-Sb-Te alloy.
Keywords: Opto-mechanics; density functional theory; dielectric function; ferroelasticity/ferroelectricity; martensitic phase transition; two-dimensional materials.