期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 115, 期 5, 页码 915-920出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1711652115
关键词
chirality; electric polarization; topological textures; resonant soft X-ray diffraction; second-principles calculations
资金
- Office of Science, Office of Basic Energy Sciences, of the US Department of Energy [DE-AC02-05CH11231]
- Office of Science, Office of Basic Energy Sciences, US Department of Energy [DE-AC02-05CH11231]
- Ramon y Cajal [RyC-2013-12515]
- Army Research Office [W911NF-14-1-0104]
- US Department of Energy, Office of Basic Energy Sciences [DE-SC0012375]
- Office of Basic Energy Sciences, US Department of Energy [DE-AC02-05CH11231]
- National Science Foundation under the Materials Research Science and Engineering Centers program [DMR-1420620]
- Luxembourg National Research Fund [C15/MS/10458889]
- Spanish Ministry of Economy and Competitiveness [FIS2015-64886-C5-2-P]
- Gordon and Betty Moore Foundation's Emergent Phenomena in Quantum Systems Initiative [GBMF5307]
Chirality is a geometrical property by which an object is not superimposable onto its mirror image, thereby imparting a handedness. Chirality determines many important properties in nature-from the strength of the weak interactions according to the electroweak theory in particle physics to the binding of enzymes with naturally occurring amino acids or sugars, reactions that are fundamental for life. In condensed matter physics, the prediction of topologically protected magnetic skyrmions and related spin textures in chiral magnets has stimulated significant research. If the magnetic dipoles were replaced by their electrical counterparts, then electrically controllable chiral devices could be designed. Complex oxide BaTiO3/SrTiO3 nanocomposites and PbTiO3/SrTiO3 superlattices are perfect candidates, since polar vortices, in which a continuous rotation of ferroelectric polarization spontaneously forms, have been recently discovered. Using resonant soft X-ray diffraction, we report the observation of a strong circular dichroism from the interaction between circularly polarized light and the chiral electric polarization texture that emerges in PbTiO3/SrTiO3 superlattices. This hallmark of chirality is explained by a helical rotation of electric polarization that second-principles simulations predict to reside within complex 3D polarization textures comprising ordered topological line defects. The handedness of the texture can be topologically characterized by the sign of the helicity number of the chiral line defects. This coupling between the optical and novel polar properties could be exploited to encode chiral signatures into photon or electron beams for information processing.
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