Multi-physics properties in ferroelectric nanostructure

Abstract

Mechanical stress/strain strongly affects and interacts with ferroelectric and various electronic properties, i.e., "Multi-Physics" coupling. Especially, ferroelectric nanostructures exhibit novel properties distinct from the bulk counterpart. This paper reviews a series of studies on remarkable ferroelectric and multi-physics properties in nanoscale components from first-principles calculations, which are essential for the nonlinear multi-physics couplings due the quantum mechanical effects. The novelty and complexity of ferroelectric nanostructures originate from combinations of the outer shape (e.g., thin film, nano-wire, tube, and dot) and the inner understructure (e.g., grain boundary, domain wall, and lattice distortion). Each shape or understructure alters spontaneous polarization although the influence is restricted within a local area of several nanometers. The multi-physics coupling with mechanical stress/strain not only enhances their influence dramatically and entirely but also brings about novel and unusual ferroelectric properties, such as ferromagnetic-like closure-nanodomains, polarization vortices, improper ferroelectricity, and absence of ferroelectric critical sizes. This paper first classifies these nanostructures into fundamental elements and explains the interplay of them systematically, which provides deeper insights into multi-physics properties in nanostructures. This review simultaneously points out a new direction of "mechanics of materials", which opens the door to exploit and design novel functionalities in the nanoscales.