Whirls and swirls of polarization

doi:10.1126/science.abg4477

GSTDTAP > 气候变化

DOI	10.1126/science.abg4477
	Whirls and swirls of polarization
	Lane W. Martin
	2021-03-05
发表期刊	Science
出版年	2021
英文摘要	In Greek mythology, sailors feared the perils of getting near the whirlpool said to be created by the sea monster Charybdis, who created turbulence by swallowing huge amounts of water. Today, researchers are creating whirlpools in materials at the nano- and microscale, not from water but from magnetic spins or electric dipoles. In return, they have observed exotic phenomena and physics. On page 1050 of this issue, Guo et al. ([ 1 ][1]) provide another example of how the exacting control of materials is producing effects one thought impossible to achieve. They created self-assembled topological and toroidal polarization textures—that is, a toroidal polarization arrangement in which the polar toroidal dipole configuration corresponds to the field of a solenoid bent into a torus (see the figure, bottom) in ferroelectric polymers. Because of the exotic structure, this material exhibits properties not observed in its native state. For some time, similar whirling structures were observed in the spins of magnetic materials. Such features include vortex structures that act as domain walls and so-called skyrmions, nanoscale whirls of smoothly evolving spin that are robust because of their topological nature ([ 2 ][2]). Such emergent-spin topologies have been widely studied and are currently being considered for high-density, ultrafast memory applications ([ 3 ][3]). In ferroelectrics (materials that have a spontaneous polarization instead of magnetization), it was not expected that such smoothly evolving, topologically protected structures would be possible because the primary order parameter (polarization) is strongly coupled to the lattice. Thus, continuous evolution of the order parameter would result in a large cost in elastic energy. Despite this limitation, theoretical predictions provided clues for overcoming these limitations to realize vortex structures ([ 4 ][4]). In turn, as experimental approaches both for synthesizing and characterizing materials and order-parameter structures at the nanoscale matured, such continuous-symmetry structures were realized in the form of polarization vortices and skyrmions in (PbTiO3) m /(SrTiO3) n superlattices ([ 5 ][5]–[ 7 ][6]), where m and n are the respective number of repeated layers in artificial stacks of different materials created with unit cell–level control. Researchers found that they could create vortices and skyrmions in superlattices by manipulating various energy scales. By controlling the electric, elastic, and gradient energies, a material could effectively occupy a state in which no single energy dominated. Nanoscale features (with typical length scales of ∼10 nm) once thought impossible were observed (see the figure, top) that had merely been hidden until the appropriate energy competitions could be produced. It was quickly realized that emergent properties and function also followed. These effects included emergent chirality ([ 8 ][7]), an exotic capacitive response ([ 9 ][8], [ 10 ][9]), and an emergent order parameter—a so-called electric toroidal moment ([ 4 ][4], [ 11 ][10]) that can also give rise to a range of phenomena, such as pyrotoroidic and piezotoroidic effects, in response to thermodynamic stimuli. ![Figure][11] Emergent polar textures In ferroelectrics (materials that have a spontaneous polarization), creating smoothly evolving, topologically protected dipole vortices must overcome large elastic energy costs. GRAPHIC: V. ALTOUNIAN/ SCIENCE Guo et al. have now extended this exciting direction in ferroelectrics to a new class of materials based on the ferroelectric polymer poly(vinylidene fluoride- ran -trifluoroethylene), or P(VDF-TrFE). Instead of heterostructured complex oxides, they formed exotic polar structures with toroidal-polar topology in a single-layer film of the polymer through self-organized alignment of the polymer chains (see the figure, bottom). This material was purposefully chosen to provide the most robust polarization. The authors used a creative melt-recrystallization process formed ring-shaped bands and a periodically undulating surface topography (which could be described as “wrinkled”). This structure produces substantial strain in a periodic fashion that ultimately provides the appropriate competition between the same electric, elastic, and gradient energies to drive the formation of a concentric, continuously rotating polar structure. It has a net axial moment that makes it toroidal. What is perhaps most unexpected is that whereas the complex-oxide superlattices produce exotic-polar topologies at the ∼10-nm length scale, Guo et al. created features at the 100- to 1000-nm length scale. This observation suggests that there are multiple length scales across which similar energy competition might produce exotic structures, and alsothat mesoscopic hierarchical-polarization textures (unit cell–level structures inside of domain-level structures) could enable exotic function. In that regard, when Guo et al. probed the properties of the system, they found that it exhibited unexpected responses. Perpendicular to the polymer chains, there is continuous rotation and the formation of a toroidal structure, but parallel to the polymer chains, unexpected relaxor-like response is observed. Relaxors are characterized by diffuse-phase transitions and frequency dispersion of dielectric response arising from the complex-polar structure and fluctuations of that structure with applied field and temperature ([ 12 ][12]). Chemical disorder, random electric fields, and coexisting local dynamics are all sources of such fluctuations in complex materials. The periodic strain on the material likely induces this range of responses to applied stimuli and the observed relaxor-like response. The authors also recognized that strong coupling between ferroelectric polarization and light should occur at the length scale of the emergent toroidal-polar topology, which would be in the terahertz range. They manipulated terahertz radiation with this material in a way that the parent material normally could not. This result could find application in terahertz optics for rastering and light modulation and motivates further design of such mesoscopic polar structures to address important needs in applications. What this study by Guo et al. and other studies in recent years have shown is that advances in our ability to make and probe materials can potentially rewrite what we think is possible. The current work shows the universality of the power of manipulating energy scales—be it in unit cell–sized superlattices or micrometer-sized polymer crystals—to carefully control the pertinent energies that can produce unexpected features. The observation of toroidal order may not only lead to exotic optical responses but could also provide for exotic electric field–induced function and the potential for new types of thermal and electromechanical responses. Also, because of the intrinsically mesoscopic nature of the polymer systems, the study by Guo et al. represents just the beginning of what could be a large design landscape in which exotic dielectric, optical, and other properties could be coaxed from these complex materials. 1. [↵][13]1. M. Guo et al ., Science 371, 1050 (2021). [OpenUrl][14][Abstract/FREE Full Text][15] 2. [↵][16]1. A. Fert, 2. N. Reyren, 3. V. Cros , Nat. Rev. Mater. 2, 17031 (2017). [OpenUrl][17] 3. [↵][18]1. N. Nagaosa, 2. Y. Tokura , Nat. Nanotechnol. 8, 899 (2013). [OpenUrl][19][CrossRef][20][PubMed][21] 4. [↵][22]1. I. I. Naumov, 2. L. Bellaiche, 3. H. Fu , Nature 432, 737 (2004). [OpenUrl][23][CrossRef][24][PubMed][25] 5. [↵][26]1. A. K. Yadav et al ., Nature 530, 198 (2016). [OpenUrl][27][CrossRef][28][PubMed][29] 6. 1. A. R. Damodaran et al ., Nat. Mater. 16, 1003 (2017). [OpenUrl][30][CrossRef][31][PubMed][32] 7. [↵][33]1. S. Das et al ., Nature 568, 368 (2019). [OpenUrl][34][CrossRef][35][PubMed][36] 8. [↵][37]1. P. Shafer et al ., Proc. Natl. Acad. Sci. U.S.A. 115, 915 (2018). [OpenUrl][38][Abstract/FREE Full Text][39] 9. [↵][40]1. A. K. Yadav et al ., Nature 565, 468 (2019). [OpenUrl][41] 10. [↵][42]1. S. Das et al ., Nat. Mater. 20, 194 (2020). [OpenUrl][43] 11. [↵][44]1. H. Schmid , J. Phys. Condens. Matter 20, 434201 (2008). [OpenUrl][45][CrossRef][46][PubMed][25] 12. [↵][47]1. R. A. Cowley, 2. S. N. Gvasaliya, 3. S. G. Lushnikov, 4. B. Roessli, 5. G. M. Rotaru , Adv. Phys. 60, 229 (2011). [OpenUrl][48][CrossRef][49][Web of Science][50] Acknowledgments: L.W.M. acknowledges support from the National Science Foundation under grant DMR-1708615. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5 [6]: #ref-7 [7]: #ref-8 [8]: #ref-9 [9]: #ref-10 [10]: #ref-11 [11]: pending:yes [12]: #ref-12 [13]: #xref-ref-1-1 "View reference 1 in text" [14]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DGuo%26rft.auinit1%253DM.%26rft.volume%253D371%26rft.issue%253D6533%26rft.spage%253D1050%26rft.epage%253D1056%26rft.atitle%253DToroidal%2Bpolar%2Btopology%2Bin%2Bstrained%2Bferroelectric%2Bpolymer%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.abc4727%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [15]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEzOiIzNzEvNjUzMy8xMDUwIjtzOjQ6ImF0b20iO3M6MjI6Ii9zY2kvMzcxLzY1MzMvOTkyLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ== [16]: #xref-ref-2-1 "View reference 2 in text" [17]: {openurl}?query=rft.jtitle%253DNat.%2BRev.%2BMater.%26rft.volume%253D2%26rft.spage%253D17031%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [18]: #xref-ref-3-1 "View reference 3 in text" [19]: {openurl}?query=rft.jtitle%253DNat.%2BNanotechnol.%26rft.volume%253D8%26rft.spage%253D899%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnnano.2013.243%26rft_id%253Dinfo%253Apmid%252F24302027%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [20]: /lookup/external-ref?access_num=10.1038/nnano.2013.243&link_type=DOI [21]: /lookup/external-ref?access_num=24302027&link_type=MED&atom=%2Fsci%2F371%2F6533%2F992.atom [22]: #xref-ref-4-1 "View reference 4 in text" [23]: {openurl}?query=rft.jtitle%253DNature%26rft.stitle%253DNature%26rft.aulast%253DNaumov%26rft.auinit1%253DI.%2BI.%26rft.volume%253D432%26rft.issue%253D7018%26rft.spage%253D737%26rft.epage%253D740%26rft.atitle%253DUnusual%2Bphase%2Btransitions%2Bin%2Bferroelectric%2Bnanodisks%2Band%2Bnanorods.%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnature03107%26rft_id%253Dinfo%253Apmid%252F15592408%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [24]: /lookup/external-ref?access_num=10.1038/nature03107&link_type=DOI [25]: /lookup/external-ref?access_num=15592408&link_type=MED&atom=%2Fsci%2F371%2F6533%2F992.atom [26]: #xref-ref-5-1 "View reference 5 in text" [27]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D530%26rft.spage%253D198%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnature16463%26rft_id%253Dinfo%253Apmid%252F26814971%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [28]: /lookup/external-ref?access_num=10.1038/nature16463&link_type=DOI [29]: /lookup/external-ref?access_num=26814971&link_type=MED&atom=%2Fsci%2F371%2F6533%2F992.atom [30]: {openurl}?query=rft.jtitle%253DNat.%2BMater.%26rft.volume%253D16%26rft.spage%253D1003%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnmat4951%26rft_id%253Dinfo%253Apmid%252F28783161%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [31]: /lookup/external-ref?access_num=10.1038/nmat4951&link_type=DOI [32]: /lookup/external-ref?access_num=28783161&link_type=MED&atom=%2Fsci%2F371%2F6533%2F992.atom [33]: #xref-ref-7-1 "View reference 7 in text" [34]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D568%26rft.spage%253D368%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fs41586-019-1092-8%26rft_id%253Dinfo%253Apmid%252F30996320%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [35]: /lookup/external-ref?access_num=10.1038/s41586-019-1092-8&link_type=DOI [36]: /lookup/external-ref?access_num=30996320&link_type=MED&atom=%2Fsci%2F371%2F6533%2F992.atom [37]: #xref-ref-8-1 "View reference 8 in text" [38]: {openurl}?query=rft.jtitle%253DProc.%2BNatl.%2BAcad.%2BSci.%2BU.S.A.%26rft_id%253Dinfo%253Adoi%252F10.1073%252Fpnas.1711652115%26rft_id%253Dinfo%253Apmid%252F29339493%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [39]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoicG5hcyI7czo1OiJyZXNpZCI7czo5OiIxMTUvNS85MTUiO3M6NDoiYXRvbSI7czoyMjoiL3NjaS8zNzEvNjUzMy85OTIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [40]: #xref-ref-9-1 "View reference 9 in text" [41]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D565%26rft.spage%253D468%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [42]: #xref-ref-10-1 "View reference 10 in text" [43]: {openurl}?query=rft.jtitle%253DNat.%2BMater.%26rft.volume%253D20%26rft.spage%253D194%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [44]: #xref-ref-11-1 "View reference 11 in text" [45]: {openurl}?query=rft.jtitle%253DJ.%2BPhys.%2BCondens.%2BMatter%26rft.volume%253D20%26rft.spage%253D434201%26rft_id%253Dinfo%253Adoi%252F10.1088%252F0953-8984%252F20%252F43%252F434201%26rft_id%253Dinfo%253Apmid%252F15592408%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [46]: /lookup/external-ref?access_num=10.1088/0953-8984/20/43/434201&link_type=DOI [47]: #xref-ref-12-1 "View reference 12 in text" [48]: {openurl}?query=rft.jtitle%253DAdv.%2BPhys.%26rft.volume%253D60%26rft.spage%253D229%26rft_id%253Dinfo%253Adoi%252F10.1080%252F00018732.2011.555385%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [49]: /lookup/external-ref?access_num=10.1080/00018732.2011.555385&link_type=DOI [50]: /lookup/external-ref?access_num=000293061900001&link_type=ISI
领域	气候变化 ; 资源环境
URL	查看原文
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/316986
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Lane W. Martin. Whirls and swirls of polarization[J]. Science,2021.
APA	Lane W. Martin.(2021).Whirls and swirls of polarization.Science.
MLA	Lane W. Martin."Whirls and swirls of polarization".Science (2021).