Structural Chirality of Polar Skyrmions Probed by Resonant Elastic X-Ray Scattering

McCarter, Margaret R.; Kim, Kook Tae; Stoica, Vladimir; Das, Sujit; Klewe, Christoph; Donoway, Elizabeth; Burn, D. M.; Shafer, Padraic; Rodolakis, Fanny; Gonçalves, M. A. P.; Gómez‐Ortiz, Fernando; Íñiguez, Jorgé; García‐Fernández, Pablo; Junquera, Javier; Lovesey, S. W.; Laan, G. van der; Park, Se Young; Freeland, J. W.; Martin, Lane W.; Lee, Dong Ryeol; Ramesh, R.

doi:10.1103/physrevlett.129.247601

Cited by 9 publications

(4 citation statements)

References 43 publications

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“…3,14−16 In contrast, polar skyrmions exist in the (PTO)/(STO) superlattice on the STO substrate, where the substrate/superlattice mismatch strain is more compressive. 6,13,17,18 In this work, we demonstrate that, without the change of elastic condition, on the same substrate, by only tuning the effective screening and depolarization degree in the superlattice, we can transform polar vortex and skyrmions into each other. By varying the thickness of STO and PTO, we can change the effective screening provided by the STO layers to the PTO layers and the depolarization degree of the PTO layers.…”

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confidence: 74%

“…Previous work has shown that the elastic boundary condition is the key factor that determines the emergence of different topological phases. The vortex phase only exists in the (PTO)/(STO) superlattice on the DyScO 3 substrate, which renders a relatively small compressing strain to the superlattice. ,− In contrast, polar skyrmions exist in the (PTO)/(STO) superlattice on the STO substrate, where the substrate/superlattice mismatch strain is more compressive. ,,, …”

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confidence: 99%

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Tuning Topology Phases by Controlling Effective Screening and Depolarization in Oxide Superlattices

Wang,

Chen

2024

Nano Lett.

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Polar topological phases in oxide superlattices attracted significant attention due to their unique properties. Previous work revealed that a polar vortex and polar skyrmions exist in (PTO)/(STO) superlattices under different elastic constraints, i.e., on different substrates. Here, our phasefield simulation demonstrates that manipulating the PTO and STO layers' thickness can control the effective screening provided by STO and the depolarization degree in PTO, thus switching the system among the polar skyrmions, vortex labyrinth, or paraelectric phase without changing elastic constraints. Additionally, reducing the STO thickness creates interlayer coupling among PTO layers, generating the long-range order of topological phases within superlattices. Furthermore, we construct a PTO−STO thickness topological phase diagram. These findings offer insights into the polar topological phases' formation in oxide superlattices, elucidating the roles of ferroelectric and paraelectric layers in their formation.

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confidence: 74%

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confidence: 99%

Tuning Topology Phases by Controlling Effective Screening and Depolarization in Oxide Superlattices

Wang,

Chen

2024

Nano Lett.

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“…Magnetic SkLs exhibit responses to external stimuli distinct from those of atomic crystal [14][15][16] , along with novel emergent properties, e.g., topological magnon band structure 17 , topological Nernst effect 18 , and novel microwave processing schemes in reconfigurable quasi-particle arrays [19][20][21] . As analogies to magnetic skyrmions, polar skyrmions in ferroelectric superlattices and multilayers [22][23][24][25][26][27][28][29] have garnered widespread attention due to similar topology but distinct properties, such as negative capacitance 30 and giant electric field-induced second harmonic generation 31 . However, they have yet to be experimentally demonstrated to form long-range ordered polar SkLs 27 , despite theoretical predictions suggesting the formation of hexagonal polar SkLs (H-SkLs) 32,33 .…”

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confidence: 99%

Emergence and Transformation of Polar Skyrmion Lattices via Flexoelectricity

Chen,

Ren,

Liu

et al. 2024

Preprint

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As analogies to magnetic skyrmions, polar skyrmions in ferroelectric superlattices and multilayers have garnered widespread attention for their non-trivial topology and novel properties like negative capacitance and nonlinear optical effect. So far, they have only been theoretically predicted to be able to assemble ordered hexagonal skyrmion lattices (SkLs) in ferroelectric thin films. Here, based on phase-field simulations, we report the critical roles of flexoelectricity playing in the stabilization and transformation of polar SkLs. Different polar SkL patterns can emerge in the ferroelectric thin films, including tetragonal-SkL, and hexagonal-SkLs with diverse orientations, as summarized by phase diagrams. These emergent SkL states are attributed to the material anisotropy modified by the flexoelectric effect. Interestingly, we further found that the hexagonal-SkLs can be rotated by applying strain gradient or in-plane electric field to the films. Moreover, a nonreciprocal bending response of tetragonal-SkL is also induced by the flexoelectric effect. Our results provide useful guidelines for the implementation of polar skyrmion lattices in experiments.

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“…To understand this, we refer to the model proposed for resonant diffraction from polar vortices, where circular dichroism is explained by the helical rotation of electric quadrupoles in the y – z planes, , where y and z are, respectively, the [010] pc and [001] pc directions. It is easy to see that electric quadrupole transitions are involved in the scattering using symmetry considerations.…”

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confidence: 99%

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

et al. 2023

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Nontrivial polarization textures have been demonstrated in ferroelectric/dielectric superlattices, where the electrostatic, elastic, and different gradient energies compete in a delicate balance. When PbTiO 3 /SrTiO 3 superlattices are grown on DyScO 3 , the coexistence of ferroelectric domains and vortex structure is observed for n = 12−20 unit cells. Here, we report an approach to achieve single-phase vortex structures in superlattices by controlling the epitaxial strain using Sr 1.04 Al 0.12 Ga 0.35 Ta 0.50 O 3 substrates. The domain width follows Kittel's law with the thickness of the ferroelectric PbTiO 3 layers. A phase transition from vortex to a disordered phase with temperature is characterized by the correlation length. Resonant soft X-ray diffraction circular dichroism at the titanium L-edge reveals enhanced chirality with the thickness of the ferroelectric layer. These results are supported by second-principles simulations, which demonstrate that the integrated helicity increases with n. The stabilization of chiral single-phase polar vortices in ferroelectric/dielectric superlattices can enable novel optoelectronic devices with enhanced ferroelectric−light interaction.

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Structural Chirality of Polar Skyrmions Probed by Resonant Elastic X-Ray Scattering

Cited by 9 publications

References 43 publications

Tuning Topology Phases by Controlling Effective Screening and Depolarization in Oxide Superlattices

Tuning Topology Phases by Controlling Effective Screening and Depolarization in Oxide Superlattices

Emergence and Transformation of Polar Skyrmion Lattices via Flexoelectricity

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

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Structural Chirality of Polar Skyrmions Probed by Resonant Elastic X-Ray Scattering

Cited by 9 publications

References 43 publications

Tuning Topology Phases by Controlling Effective Screening and Depolarization in Oxide Superlattices

Tuning Topology Phases by Controlling Effective Screening and Depolarization in Oxide Superlattices

Emergence and Transformation of Polar Skyrmion Lattices via Flexoelectricity

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

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Product

Resources

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