Local negative permittivity and topological phase transition in polar skyrmions

Das, Sujit; Hong, Zijian; Stoica, Vladimir; Gonçalves, M. A. P.; Shao, Yu‐Tsun; Parsonnet, Eric; Marksz, Eric J.; Saremi, Sahar; McCarter, Margaret R.; Reynoso, A.; Long, Christian J.; Hagerstrom, Aaron M.; Meyers, D.; Ravi, Vishal; Prasad, Bhagwati; Zhou, Hao; Zhang, Z.; Wen, Haidan; Gómez‐Ortiz, Fernando; García‐Fernández, Pablo; Bokor, J.; Íñiguez, Jorgé; Freeland, J. W.; Orloff, Nathan D.; Junquera, Javier; Chen, L. Q.; Salahuddin, Sayeef; Muller, David A.; Martin, Lane W.; Ramesh, R.

doi:10.1038/s41563-020-00818-y

Cited by 128 publications

(97 citation statements)

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“…Ferroelectrics have long been studied due to its switchable polarizations and thus are promising for a plethora of applications such as in electromechanical systems, [1,2] multiferroics systems, [3][4][5][6][7] and memory/energy storage systems. [8][9][10][11][12][13][14][15] Ferroelectric materials, in particular, perovskites ferroelectrics [8] such as Pb(Zr,Ti)O 3 (PZT), [16][17][18] BaTiO 3 , [19][20][21] and SrBi 2 Ta 2 O 9 [22,23] have been widely studied.…”

Section: Introductionmentioning

confidence: 99%

An Overview of Ferroelectric Hafnia and Epitaxial Growth

Cao

Shi

Zhu

et al. 2021

Physica Rapid Research Ltrs

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Hafnia thin films have been under intensive research during the past few years due to its robust ferroelectricity under very thin limit and good compatibility with silicon. The polar crystal structure critical to ferroelectricity in hafnia thin films is metastable, and is generally obtained in polycrystalline thin films, coexisting with other nonpolar phases. Recently, much attention has been focused on epitaxial ferroelectric hafnia thin films to get rid of the nonpolar phases, to investigate the more intrinsic factors to ferroelectricity, and its potential applications. Herein, recent progress on the growth of epitaxial hafnia thin films is reviewed. The epitaxial growth mechanism is explored, in particular, the interface matching, phase stability under temperature and oxygen pressure, followed by discussions on thickness dependency of ferroelectricity, and wake-up effect in hafnia. Finally, an outlook on ferroelectric hafnia both on fundamental studies and future applications is discussed.

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Section: Introductionmentioning

confidence: 99%

An Overview of Ferroelectric Hafnia and Epitaxial Growth

Cao

Shi

Zhu

et al. 2021

Physica Rapid Research Ltrs

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“…Note that some recent works have reported the presence of a negative capacitance (NC) state in ferroelectric – dielectric heterostructures. [ 7–9 ] As the voltage is increased from 0, such NC states (if there is any) are expected to convert into positive capacitance state. Therefore, total capacitance should either increase (when NC is in parallel with the positive capacitance) or decrease (when NC is in series with the positive capacitance) as the voltage is increased from 0.…”

Section: Resultsmentioning

confidence: 99%

“…The intricate and competing correlations among elastic,electrostatic, and gradient energies in ferroelectric (FE)–dielectric (DE)–FE heterostructures create topological objects with complex polar order, such as vortices, bubbles, and skyrmions. [ 1–4 ] The inherent nontrivial electromechanical inhomogeneities in these topological objects promote a plethora of novel physical phenomena such as negative capacitance, [ 5–9 ] flexoelectric effects, [ 10 ] emergent chirality, [ 11 ] and gradual conductivity hysteresis [ 12,13 ] which have tremendous potential in future computing and sensing technologies. The parameter space (epitaxial strain, screening, built‐in field, etc.)…”

Section: Introductionmentioning

confidence: 99%

Freestanding Ferroelectric Bubble Domains

et al. 2021

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Bubble‐like domains, typically a precursor to the electrical skyrmions, arise in ultrathin complex oxide ferroelectric–dielectric–ferroelectric heterostructures epitaxially clamped with flat substrates. Here, it is reported that these specially ordered electric dipoles can also be retained in a freestanding state despite the presence of inhomogeneously distributed structural ripples. By probing local piezo and capacitive responses and using atomistic simulations, this study analyzes these ripples, sheds light on how the bubbles are stabilized in the modified electromechanical energy landscape, and discusses the difference in morphology between bubbles in freestanding and as‐grown states. These results are anticipated to be the starting point of a new paradigm for the exploration of electric skyrmions with arbitrary boundaries and physically flexible topological orders in ferroelectric curvilinear space.

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“…pitaxial complex oxide heterostructures and superlattices with their interplay of spin, charge, orbital and lattice degrees of freedom offer a rich platform to study exotic phenomena such as spin-charge transfer, multiferroicity, and unique topological phases 1 . With careful manipulation of the elastic, electrostatic and gradient energies, topological structures such as polar flux-closure domains 2,3 , vortices [4][5][6][7] , bubble domains 8,9 and skyrmions 10,11 , can be formed in epitaxially grown (PbTiO 3 ) n /(SrTiO 3 ) n (PTO/STO) superlattices and other ferroelectric nanocomposites 12 . In particular, polar vortices, i.e., smoothly rotating electric dipoles, are interesting for their spatially confined negative capacitance 13 and chirality 14 .…”

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confidence: 99%

Atomic scale crystal field mapping of polar vortices in oxide superlattices

et al. 2021

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Polar vortices in oxide superlattices exhibit complex polarization topologies. Using a combination of electron energy loss near-edge structure analysis, crystal field multiplet theory, and first-principles calculations, we probe the electronic structure within such polar vortices in [(PbTiO3)16/(SrTiO3)16] superlattices at the atomic scale. The peaks in Ti $$L$$ L -edge spectra shift systematically depending on the position of the Ti4+ cations within the vortices i.e., the direction and magnitude of the local dipole. First-principles computation of the local projected density of states on the Ti $$3d$$ 3 d orbitals, together with the simulated crystal field multiplet spectra derived from first principles are in good agreement with the experiments.

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Local negative permittivity and topological phase transition in polar skyrmions

Cited by 128 publications

References 50 publications

An Overview of Ferroelectric Hafnia and Epitaxial Growth

An Overview of Ferroelectric Hafnia and Epitaxial Growth

Freestanding Ferroelectric Bubble Domains

Atomic scale crystal field mapping of polar vortices in oxide superlattices

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