In-Plane Chirality Control of a Charge Density Wave by Means of Shear Stress

The transition metal dichalcogenide 1T-TaS₂ exhibits a Charge Density Wave (CDW) with in-plane chirality. Due to the rich phase diagram, the Ferro-Rotational Order (FRO) can be tuned by external stimuli. The FRO is studied by Angle-Resolved Photoelectron Spectroscopy (ARPES), Raman spectroscopy, and Selected Area Electron Diffraction (SAED). The in-plane chirality of the CDW is lost at the transition from Nearly-Commensurate (NC) to In-Commensurate (IC) phase and can be controlled by applying shear stress to the sample while cooling it through the transition from IC-CDW to NC-CDW. Based on these observations, a protocol is proposed to achieve reliable, non-volatile state switching of the FRO configuration in 1T-TaS₂ bulk crystals. These results pave the way for new functional devices in which in-plane chirality can be set on demand.