For low-dimensional atomic scale materials, a small amount of compressive load would easily lead to Euler's buckling instability. Thus, it is very challenging to reach the compressive strain regime in the phase diagram, and of course one may lose a lot of tremendous properties. Collaborated with Prof. Sheng Mao at Peking University, Prof. Shunhong Zhang at USTC, we propose a new mechanism to realize intrinsic strains (can be both tensile and compressive) under light illumination. This is a nonlinear coupling between light and the acoustic phonon branch, serving as a compensation of our group's previous theory of optomechanical phase transition, which is a coupling between light and optical phonon branch. We use a well-studied Z₂ TI, transition metal dichalcogenide monolayer, to illustrate this theory. According to the thermodynamic theory between optical electric field and lattice degrees of freedom, the 1T' TMDC monolayer could exhibit a large compressive strain of over 1% under intermediate light intensity. Large anisotropic optostrictive responses are also predicted. The real space distribution of light intensity may lead to in-plane optoflexoelectricity.

The work has been published in Physical Review Research as a Rapid Communication. See https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.022059