First-principles prediction of optomechanically controlling phase transition of IV-VI semiconductors

Diffusional phase-change materials, such as Ge-Sb-Te alloys, are used in rewritable nonvolatile memory devices (PC-RAM). This order-disorder transition contains a large latent heat and requires breaking of chemical bonds. It is thus highly desired to develop new phase change materials with diffusionless and order-to-order transitions to accelerate the read/write kinetics, reduce energy dissipation, and eliminate fatigue. Two-dimensional materials are considered as potential phase change materials. For example, one famous 2D material example is transition metal dichalcogenide monolayer which exists in 2H and 1T′ structures. However, it always requires mechanical, electrical, or electrochemical contacts and patterning to trigger phase transition. Non-contacting optical readout/write with focused laser would be preferable in many circumstances, especially for low-dimensional materials which are easily optically accessible. Here, we computationally illustrate an optomechanical strategy, which uses a linearly polarized laser pulse with selected frequency. We will give a few examples of such ultrafast diffusionless martensitic phase transition in various materials. With no or only a few chemical bonds breaking, the phase transition would occur very fast and requires low energy input.