Emergent Ferroelectric Switching Behavior from Polar Vortex Lattice

Abstract

Topologically protected polar textures have provided a rich playground for the exploration of novel, emergent phenomena. Recent discoveries indicate that ferroelectric vortices and skyrmions not only host properties markedly different from traditional ferroelectrics, but also that these properties can be harnessed for unique memory devices. Using a combination of capacitor‐based capacitance measurements and computational models, it is demonstrated that polar vortices in dielectric–ferroelectric–dielectric trilayers exhibit classical ferroelectric bi‐stability together with the existence of low‐field metastable polarization states. This behavior is directly tied to the in‐plane vortex ordering, and it is shown that it can be used as a new method of non‐destructive readout‐out of the poled state.

Interlayer Coupling Controlled Ordering and Phases in Polar Vortex Superlattices

“…Here, the bright contrast corresponds to the stronger IP piezoresponse of the ferroelectric a 1 / a 2 phase compared to the small axial polarization component of the vortex phase along the [10] o . In Figure c, with polarization measured along the [001] o direction, this contrast between the two phases is partially lost as the a 1 / a 2 polarization is now compared to the stronger, lateral polarization component from the buckling of the vortex phase. , At a critical thickness m ≥ 30 unit cells, this structure condenses into a single vortex phase (Figure d) with domains comparable to those previously observed in STO/PTO/STO trilayers . This is in close agreement with XRD data, and thus we hypothesize that this threshold thickness ( m = 30) is where the dielectric screening of the STO quenches the interaction between adjacent PTO layers, breaking the bistability of the ferroelectric and vortex phases.…”

Pure Chiral Polar Vortex Phase in PbTiO3/SrTiO3 Superlattices with Tunable Circular Dichroism

“…Second, the in-plane strain imposed by the substrate might induce an offset between the center of the clockwise and counterclockwise vortices that leads to a mismatch in the polarization pointing in the direction where the vortices are periodic. If this offset is combined with small disproportion of the up and down domain sizes, then an excess/deficit of the clockwise/counterclockwise rotations is generated making the whole system chiral. , In our superlattices, this second mechanism is expected to be smaller than the first one, since the strain imposed by the SGAT is smaller than that in DSO. The chirality can be experimentally probed with resonant soft X-ray diffraction (RSXD), a technique that combines diffraction and X-ray absorption spectroscopy, and provides an element- and orbital-specific probe of ordered phases, such as the polar vortex phase (details in the Supporting Information).…”