Emergent chirality in the electric polarization texture of titanate superlattices

Padraic Shafer; Pablo García-Fernández; Pablo Aguado-Puente; Anoop R. Damodaran; Ajay K. Yadav; Christopher T. Nelson; Shang Lin Hsu; Jacek C. Wojdeł; Jorge Iñiguez; Lane W. Martin; Elke Arenholz; Javier Junquera; Ramamoorthy Ramesh

doi:10.1073/pnas.1711652115

Emergent chirality in the electric polarization texture of titanate superlattices

Padraic Shafer, Pablo García-Fernández, Pablo Aguado-Puente, Anoop R. Damodaran, Ajay K. Yadav, Christopher T. Nelson, Shang Lin Hsu, Jacek C. Wojdeł, Jorge Iñiguez, Lane W. Martin, Elke Arenholz, Javier Junquera, Ramamoorthy Ramesh

Research output: Contribution to journal › Article › peer-review

123 Scopus citations

Abstract

Chirality is a geometrical property by which an object is not super-imposable 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.

Original language	English (US)
Pages (from-to)	915-920
Number of pages	6
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	115
Issue number	5
DOIs	https://doi.org/10.1073/pnas.1711652115
State	Published - Jan 30 2018
Externally published	Yes

Bibliographical note

Funding Information:
We acknowledge discussions with Gerrit van der Laan, Maurits W. Haverkort, and Fernando Etayo. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract DE-AC02-05CH11231. Electron microscopy of superlattice structures was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Office of Science, Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. P.G.-F. recognizes support from Ramón y Cajal Grant RyC-2013-12515. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104 and the US Department of Energy, Office of Basic Energy Sciences under Grant DE-SC0012375 for synthesis and structural study of the materials. A.K.Y. and C.T.N. were supported by the Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. S.-L.H. acknowledges support from the National Science Foundation under the Materials Research Science and Engineering Centers program under Grant DMR-1420620. J.Í. acknowledges support from the Luxembourg National Research Fund under Grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through Grant FIS2015-64886-C5-2-P. R.R. and L.W.M. acknowledge support from the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative, under Grant GBMF5307.

Funding Information:
ACKNOWLEDGMENTS. We acknowledge discussions with Gerrit van der Laan, Maurits W. Haverkort, and Fernando Etayo. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract DE-AC02-05CH11231. Electron microscopy of superlattice structures was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Office of Science, Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. P.G.-F. recognizes support from Ramón y Cajal Grant RyC-2013-12515. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104 and the US Department of Energy, Office of Basic Energy Sciences under Grant DE-SC0012375 for synthesis and structural study of the materials. A.K.Y. and C.T.N. were supported by the Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. S.-L.H. acknowledges support from the National Science Foundation under the Materials Research Science and Engineering Centers program under Grant DMR-1420620. J.Í. acknowledges support from the Luxembourg National Research Fund under Grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through Grant FIS2015-64886-C5-2-P. R.R. and L.W.M. acknowledge support from the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative, under Grant GBMF5307.

Keywords

Chirality
Electric polarization
Resonant soft X-ray diffraction
Second-principles calculations
Topological textures

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Shafer, P., García-Fernández, P., Aguado-Puente, P., Damodaran, A. R., Yadav, A. K., Nelson, C. T., Hsu, S. L., Wojdeł, J. C., Iñiguez, J., Martin, L. W., Arenholz, E., Junquera, J., & Ramesh, R. (2018). Emergent chirality in the electric polarization texture of titanate superlattices. Proceedings of the National Academy of Sciences of the United States of America, 115(5), 915-920. https://doi.org/10.1073/pnas.1711652115

Shafer, P, García-Fernández, P, Aguado-Puente, P, Damodaran, AR, Yadav, AK, Nelson, CT, Hsu, SL, Wojdeł, JC, Iñiguez, J, Martin, LW, Arenholz, E, Junquera, J & Ramesh, R 2018, 'Emergent chirality in the electric polarization texture of titanate superlattices', Proceedings of the National Academy of Sciences of the United States of America, vol. 115, no. 5, pp. 915-920. https://doi.org/10.1073/pnas.1711652115

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abstract = "Chirality is a geometrical property by which an object is not super-imposable 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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note = "Funding Information: We acknowledge discussions with Gerrit van der Laan, Maurits W. Haverkort, and Fernando Etayo. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract DE-AC02-05CH11231. Electron microscopy of superlattice structures was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Office of Science, Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. P.G.-F. recognizes support from Ram{\'o}n y Cajal Grant RyC-2013-12515. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104 and the US Department of Energy, Office of Basic Energy Sciences under Grant DE-SC0012375 for synthesis and structural study of the materials. A.K.Y. and C.T.N. were supported by the Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. S.-L.H. acknowledges support from the National Science Foundation under the Materials Research Science and Engineering Centers program under Grant DMR-1420620. J.{\'I}. acknowledges support from the Luxembourg National Research Fund under Grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through Grant FIS2015-64886-C5-2-P. R.R. and L.W.M. acknowledge support from the Gordon and Betty Moore Foundation{\textquoteright}s Emergent Phenomena in Quantum Systems Initiative, under Grant GBMF5307. Funding Information: ACKNOWLEDGMENTS. We acknowledge discussions with Gerrit van der Laan, Maurits W. Haverkort, and Fernando Etayo. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract DE-AC02-05CH11231. Electron microscopy of superlattice structures was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Office of Science, Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. P.G.-F. recognizes support from Ram{\'o}n y Cajal Grant RyC-2013-12515. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104 and the US Department of Energy, Office of Basic Energy Sciences under Grant DE-SC0012375 for synthesis and structural study of the materials. A.K.Y. and C.T.N. were supported by the Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. S.-L.H. acknowledges support from the National Science Foundation under the Materials Research Science and Engineering Centers program under Grant DMR-1420620. J.{\'I}. acknowledges support from the Luxembourg National Research Fund under Grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through Grant FIS2015-64886-C5-2-P. R.R. and L.W.M. acknowledge support from the Gordon and Betty Moore Foundation{\textquoteright}s Emergent Phenomena in Quantum Systems Initiative, under Grant GBMF5307.",

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T1 - Emergent chirality in the electric polarization texture of titanate superlattices

AU - Shafer, Padraic

AU - García-Fernández, Pablo

AU - Aguado-Puente, Pablo

AU - Damodaran, Anoop R.

AU - Yadav, Ajay K.

AU - Nelson, Christopher T.

AU - Hsu, Shang Lin

AU - Wojdeł, Jacek C.

AU - Iñiguez, Jorge

AU - Martin, Lane W.

AU - Arenholz, Elke

AU - Junquera, Javier

AU - Ramesh, Ramamoorthy

N1 - Funding Information: We acknowledge discussions with Gerrit van der Laan, Maurits W. Haverkort, and Fernando Etayo. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract DE-AC02-05CH11231. Electron microscopy of superlattice structures was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Office of Science, Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. P.G.-F. recognizes support from Ramón y Cajal Grant RyC-2013-12515. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104 and the US Department of Energy, Office of Basic Energy Sciences under Grant DE-SC0012375 for synthesis and structural study of the materials. A.K.Y. and C.T.N. were supported by the Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. S.-L.H. acknowledges support from the National Science Foundation under the Materials Research Science and Engineering Centers program under Grant DMR-1420620. J.Í. acknowledges support from the Luxembourg National Research Fund under Grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through Grant FIS2015-64886-C5-2-P. R.R. and L.W.M. acknowledge support from the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative, under Grant GBMF5307. Funding Information: ACKNOWLEDGMENTS. We acknowledge discussions with Gerrit van der Laan, Maurits W. Haverkort, and Fernando Etayo. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract DE-AC02-05CH11231. Electron microscopy of superlattice structures was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Office of Science, Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. P.G.-F. recognizes support from Ramón y Cajal Grant RyC-2013-12515. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104 and the US Department of Energy, Office of Basic Energy Sciences under Grant DE-SC0012375 for synthesis and structural study of the materials. A.K.Y. and C.T.N. were supported by the Office of Basic Energy Sciences, US Department of Energy under Contract DE-AC02-05CH11231. S.-L.H. acknowledges support from the National Science Foundation under the Materials Research Science and Engineering Centers program under Grant DMR-1420620. J.Í. acknowledges support from the Luxembourg National Research Fund under Grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through Grant FIS2015-64886-C5-2-P. R.R. and L.W.M. acknowledge support from the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative, under Grant GBMF5307.

PY - 2018/1/30

Y1 - 2018/1/30

N2 - Chirality is a geometrical property by which an object is not super-imposable 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.

AB - Chirality is a geometrical property by which an object is not super-imposable 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.

KW - Chirality

KW - Electric polarization

KW - Resonant soft X-ray diffraction

KW - Second-principles calculations

KW - Topological textures

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Emergent chirality in the electric polarization texture of titanate superlattices

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