Manipulating topological transformations of polar structures through real-time observation of the dynamic polarization evolution

Du, Kai; Zhang, M.; Dai, Cheng; Zhou, Zheng-Nan; Xie, Yanwu; Ren, Zhaohui; Tian, He; Chen, L. Q.; Tendeloo, Gustaaf Van; Zhang, Z.

doi:10.1038/s41467-019-12864-5

Cited by 78 publications

(67 citation statements)

References 60 publications

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“…3b–d shows distributions of strain components estimated from geometric phase analysis based on the STEM image. The white-colored sinusoidal wave-like out-of-plane strain pattern is observed within PTO layers along the [100] direction, suggesting the existence of long-range vortex ordering consistent with previous reports 21 , 22 , 31 . The dark field transmission electron microscopy (TEM) image shown in Fig.…”

Section: Resultssupporting

confidence: 90%

Creating polar antivortex in PbTiO3/SrTiO3 superlattice

et al. 2021

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Nontrivial topological structures offer a rich playground in condensed matters and promise alternative device configurations for post-Moore electronics. While recently a number of polar topologies have been discovered in confined ferroelectric PbTiO3 within artificially engineered PbTiO3/SrTiO3 superlattices, little attention was paid to possible topological polar structures in SrTiO3. Here we successfully create previously unrealized polar antivortices within the SrTiO3 of PbTiO3/SrTiO3 superlattices, accomplished by carefully engineering their thicknesses guided by phase-field simulation. Field- and thermal-induced Kosterlitz–Thouless-like topological phase transitions have also been demonstrated, and it was discovered that the driving force for antivortex formation is electrostatic instead of elastic. This work completes an important missing link in polar topologies, expands the reaches of topological structures, and offers insight into searching and manipulating polar textures.

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Section: Resultssupporting

confidence: 90%

Creating polar antivortex in PbTiO3/SrTiO3 superlattice

et al. 2021

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“…As such, the vortex must be charged to the same extent as the H-H DW in Figure 2, with average = 1.09 e per PK-cell. Although the DW width is similar to the H-H case in Figure 2, the defined vortex polarisation suggests the charge density is concentrated at the vortex core [47], further increasing the relative conductivity difference versus the domain.…”

Section: Resultsmentioning

confidence: 72%

Polar Vortexes and Charged Domain Walls in a Room Temperature Magnetoelectric Thin Film

Moore¹,

O’Connell²,

Keeney³

et al. 2020

Preprint

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Multiferroic domain walls are an emerging solution for future low-power nanoelectronics due to their combined tuneable functionality and mobility. Here we show that the magnetoelectric multiferroic Aurivillius phase Bi6TixFeyMnzO18 (B6TFMO) crystal is an ideal platform for domain wall-based nanoelectronic devices. The unit cell of B6TFMO is distinctive as it consists of a multiferroic layer between dielectric layers. We utilise atomic resolution scanning transmission electron microscopy and spectroscopy to map the sub-unit-cell polarisation in B6TFMO thin films. 180˚ charged head-to-head and tail-to-tail domain walls are found to pass through > 8 ferroelectric-dielectric layers of the film. They are structurally similar to BiFeO3 DWs but contain a large surface charge density (σ_s) = 1.09 |e|per perovskite cell, where |e| is elementary charge. Although polarisation is primarily in-plane, c-axis polarisation is identified at head-to-tail domain walls with an associated electromechanical coupling of strain and polarisation. Finally, we reveal that with controlled strain engineering during thin film growth, room-temperature vortexes are formed in the ferroelectric layer. These results confirm that sub-unit-cell topological features can play an important role in controlling the conduction properties and magnetisation state of Aurivillius phase films and other multiferroic heterostructures.

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“…Damodaran et al (29) found phase coexistence of vortex and ferroelectric phases and electric-field-driven interconversion between them. Du et al (30) reported that vortices can split, transform to polar waves, and finally become a stable c domain that does not recover spontaneously. According to Chen et al (31), under mechanical stress, a polar vortex can be switched to an a domain and reversibly recover after removal of stress.…”

Section: Discussionmentioning

confidence: 99%

“…Phase-field simulations have demonstrated the possibility of switching polar vortices: under the application of an electrical field, vortex cores with opposite curls move closer until they reach the same lateral position and then produce new a domains, and the reverse process of back-switching takes place when the applied field is removed ( 37 ). The evolution of vortices driven by temperature change ( 29 ), electric field, and stress have been probed experimentally by X-ray diffraction, PFM ( 29 ), and TEM ( 30 , 31 ). Damodaran et al ( 29 ) found phase coexistence of vortex and ferroelectric phases and electric-field-driven interconversion between them.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, surface probe-based PFM is usually limited in its spatial resolution and does not have the capability to obtain full information regarding nanosized polar topological structures, which have highly structured inhomogeneities and strong charge–lattice coupling, hidden within thin films. By contrast, recent advances in atomically resolved in situ scanning transmission electron microscopy (STEM) have presented the possibility of capturing structural evolutions of individual polar vortices ( 30 , 31 ). Therefore, in the present study we utilize this cutting-edge technique to investigate whether or not topological polar flux-closures can be controllably switched to ordinary ferroelectric domains, and we further reveal the detailed transition behavior and underlying mechanism by combining this experimental investigation with phase field simulations.…”

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confidence: 99%

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Atomic-scale observations of electrical and mechanical manipulation of topological polar flux closure

Tan

Liu

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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The ability to controllably manipulate complex topological polar configurations such as polar flux-closures via external stimuli may allow the construction of new electromechanical and nanoelectronic devices. Here, using atomically resolved in situ scanning transmission electron microscopy, we find that the polar flux-closures in PbTiO3/SrTiO3 superlattice films are mobile and can be reversibly switched to ordinary single ferroelectric c or a domains under an applied electric field or stress. Specifically, the electric field initially drives movement of a flux-closure via domain wall motion and then breaks it to form intermediate a/c striped domains, whereas mechanical stress first squeezes the core of a flux-closure toward the interface and then form a/c domains with disappearance of the core. After removal of the external stimulus, the flux-closure structure spontaneously recovers. These observations can be precisely reproduced by phase field simulations, which also reveal the evolutions of the competing energies during phase transitions. Such reversible switching between flux-closures and ordinary ferroelectric states provides a foundation for potential electromechanical and nanoelectronic applications.

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Manipulating topological transformations of polar structures through real-time observation of the dynamic polarization evolution

Cited by 78 publications

References 60 publications

Creating polar antivortex in PbTiO3/SrTiO3 superlattice

Creating polar antivortex in PbTiO3/SrTiO3 superlattice

Polar Vortexes and Charged Domain Walls in a Room Temperature Magnetoelectric Thin Film

Atomic-scale observations of electrical and mechanical manipulation of topological polar flux closure

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