Subterahertz collective dynamics of polar vortices
| Autor: | Takahiro Sato, Yakun Yuan, Matthias C. Hoffmann, Cheng Dai, Tiannan Yang, Ramamoorthy Ramesh, Matthieu Chollet, Donald A. Walko, Haidan Wen, Qian Li, Ajay K. Yadav, Yi Zhu, Hyeon Jun Lee, Shukai Yu, John W. Freeland, Diling Zhu, Jirka Hlinka, Paul G. Evans, Silke Nelson, Lane W. Martin, Michael Kozina, Christelle Kadlec, Youngjun Ahn, Vladimir Stoica, Marek Paściak, Venkatraman Gopalan, Aaron M. Lindenberg, Margaret McCarter, Sujit Das, Samuel D. Marks, Suji Park, Long Qing Chen |
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| Rok vydání: | 2021 |
| Předmět: |
Diffraction
Physics Condensed Matter - Materials Science Multidisciplinary Condensed matter physics Condensed Matter - Mesoscale and Nanoscale Physics General Science & Technology Materials Science (cond-mat.mtrl-sci) FOS: Physical sciences 02 engineering and technology Vorticity 021001 nanoscience & nanotechnology Polarization (waves) 01 natural sciences Vortex Topological defect Polar vortex 0103 physical sciences Femtosecond Mesoscale and Nanoscale Physics (cond-mat.mes-hall) 010306 general physics 0210 nano-technology Excitation |
| Zdroj: | Nature, vol 592, iss 7854 |
| Popis: | The collective dynamics of topological structures1-6 are of interest from both fundamental and applied perspectives. For example, studies of dynamical properties of magnetic vortices and skyrmions3,4 have not only deepened our understanding of many-body physics but also offered potential applications in data processing and storage7. Topological structures constructed from electrical polarization, rather than electron spin, have recently been realized in ferroelectric superlattices5,6, and these are promising for ultrafast electric-field control of topological orders. However, little is known about the dynamics underlying the functionality of such complex extended nanostructures. Here, using terahertz-field excitation and femtosecond X-ray diffraction measurements, we observe ultrafast collective polarization dynamics that are unique to polar vortices, with orders-of-magnitude higher frequencies and smaller lateral size than those of experimentally realized magnetic vortices3. A previously unseen tunable mode, hereafter referred to as a vortexon, emerges in the form of transient arrays of nanoscale circular patterns of atomic displacements, which reverse their vorticity on picosecond timescales. Its frequency is considerably reduced (softened) at a critical strain, indicating a condensation (freezing) of structural dynamics. We use first-principles-based atomistic calculations and phase-field modelling to reveal the microscopic atomic arrangements and corroborate the frequencies of the vortex modes. The discovery of subterahertz collective dynamics in polar vortices opens opportunities for electric-field-driven data processing in topological structures with ultrahigh speed and density. |
| Databáze: | OpenAIRE |
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