Electrical switching of ferro-rotational order in nano-thick 1T-TaS$_2$ crystals

Abstract

Hysteretic switching of domain states is a salient character of all ferroic materials and the foundation for their multifunctional applications. Ferro-rotational order is emerging as a new type of ferroic order featuring structural rotations, but its controlled switching remains elusive due to its invariance under both time reversal and spatial inversion. Here, we demonstrate electrical switching of ferro-rotational domain states in nanometer-thick 1T -TaS 2 crystals in its charge-density-wave phases. Cooling from the high-symmetry phase to the ferrorotational phase under an external electric field induces domain state switching and domain wall formation, realized in a simple two-terminal configuration using a volt-scale voltage. Although the electric field does not couple with the order due to symmetry mismatch, it drives domain wall propagation to give rise to reversible, durable, and nonvolatile isothermal state switching at room temperature. These results pave the path for manipulation of the ferro-rotational order and its nanoelectronic applications. MainFerroic orders arise from symmetry-breaking phase transitions, finding applications in wide-ranging advanced technologies [1]. Symmetry therefore provides a powerful guide to the identification of conjugate fields that couple with and even switch the orders -a prerequisite for utilizing the associated multi-stable domain states [2]. This principle is well applicable to three out of the four types of ferroics with a vector order parameter [2]: ferromagnets (ferroelectrics) feature time-reversal (spatial-inversion) symmetry breaking spontaneous magnetization (electric polarization) that is switchable by a magnetic (electric) field, whereas the ferro-toroidal order breaks both symmetries and can be switched using composite magnetic and electric fields [3][4][5]. The remaining type -the ferro-rotational (also known as ferroaxial) order -stands out, as it is both time-reversal and spatial-inversion invariant, hence insensitive to electromagnetic fields [2,6]. The lack of external fields that hysteretically switch the ferro-rotational order casts doubts on its ferroic nature [7] and limits its potential applications.