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Das S, McCarter MR, Gómez-Ortiz F, Tang YL, Hong Z, Ghosh A, Shafer P, García-Fernández P, Junquera J, Martin LW, Ramesh R. Pure Chiral Polar Vortex Phase in PbTiO 3/SrTiO 3 Superlattices with Tunable Circular Dichroism. NANO LETTERS 2023. [PMID: 37449842 DOI: 10.1021/acs.nanolett.3c01744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
Nontrivial polarization textures have been demonstrated in ferroelectric/dielectric superlattices, where the electrostatic, elastic, and different gradient energies compete in a delicate balance. When PbTiO3/SrTiO3 superlattices are grown on DyScO3, the coexistence of ferroelectric domains and vortex structure is observed for n = 12-20 unit cells. Here, we report an approach to achieve single-phase vortex structures in superlattices by controlling the epitaxial strain using Sr1.04Al0.12Ga0.35Ta0.50O3 substrates. The domain width follows Kittel's law with the thickness of the ferroelectric PbTiO3 layers. A phase transition from vortex to a disordered phase with temperature is characterized by the correlation length. Resonant soft X-ray diffraction circular dichroism at the titanium L-edge reveals enhanced chirality with the thickness of the ferroelectric layer. These results are supported by second-principles simulations, which demonstrate that the integrated helicity increases with n. The stabilization of chiral single-phase polar vortices in ferroelectric/dielectric superlattices can enable novel optoelectronic devices with enhanced ferroelectric-light interaction.
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Affiliation(s)
- Sujit Das
- Materials Research Centre, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Margaret R McCarter
- Department of Materials Science & Engineering, University of California, Berkeley, California 94720, United States
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Fernando Gómez-Ortiz
- Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Avenida de los Castros s/n, E-39005 Santander, Spain
| | - Yun-Long Tang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Zijian Hong
- School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Anirban Ghosh
- Department of Materials Science & Engineering, University of California, Berkeley, California 94720, United States
| | - Padraic Shafer
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Pablo García-Fernández
- Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Avenida de los Castros s/n, E-39005 Santander, Spain
| | - Javier Junquera
- Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Avenida de los Castros s/n, E-39005 Santander, Spain
| | - Lane W Martin
- Department of Materials Science & Engineering, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ramamoorthy Ramesh
- Department of Materials Science & Engineering, University of California, Berkeley, California 94720, United States
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Materials Science and Nanoengineering, Department of Physics and Astronomy, Rice University, Houston, Texas 77251, United States
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McCarter MR, Kim KT, Stoica VA, Das S, Klewe C, Donoway EP, Burn DM, Shafer P, Rodolakis F, Gonçalves MAP, Gómez-Ortiz F, Íñiguez J, García-Fernández P, Junquera J, Lovesey SW, van der Laan G, Park SY, Freeland JW, Martin LW, Lee DR, Ramesh R. Structural Chirality of Polar Skyrmions Probed by Resonant Elastic X-Ray Scattering. PHYSICAL REVIEW LETTERS 2022; 129:247601. [PMID: 36563236 DOI: 10.1103/physrevlett.129.247601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 03/08/2022] [Accepted: 10/23/2022] [Indexed: 06/17/2023]
Abstract
An escalating challenge in condensed-matter research is the characterization of emergent order-parameter nanostructures such as ferroelectric and ferromagnetic skyrmions. Their small length scales coupled with complex, three-dimensional polarization or spin structures makes them demanding to trace out fully. Resonant elastic x-ray scattering (REXS) has emerged as a technique to study chirality in spin textures such as skyrmions and domain walls. It has, however, been used to a considerably lesser extent to study analogous features in ferroelectrics. Here, we present a framework for modeling REXS from an arbitrary arrangement of charge quadrupole moments, which can be applied to nanostructures in materials such as ferroelectrics. With this, we demonstrate how extended reciprocal space scans using REXS with circularly polarized x rays can probe the three-dimensional structure and chirality of polar skyrmions. Measurements, bolstered by quantitative scattering calculations, show that polar skyrmions of mixed chirality coexist, and that REXS allows valuation of relative fractions of right- and left-handed skyrmions. Our quantitative analysis of the structure and chirality of polar skyrmions highlights the capability of REXS for establishing complex topological structures toward future application exploits.
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Affiliation(s)
- Margaret R McCarter
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Kook Tae Kim
- Department of Physics, Soongsil University, Seoul 06978, Korea
| | - Vladimir A Stoica
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
- Department of Materials Science and Engineering, Pennsylvania State University, Pennsylvania 16802, USA
| | - Sujit Das
- Materials Research Centre, Indian Institute of Science, Bangalore 560012, India
| | - Christoph Klewe
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Elizabeth P Donoway
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - David M Burn
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Padraic Shafer
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Fanny Rodolakis
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Mauro A P Gonçalves
- Institute of Physics of the Czech Academy of Sciences, 18221 Prague 8, Czech Republic
| | - Fernando Gómez-Ortiz
- Departmento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, 39005 Santander, Spain
| | - Jorge Íñiguez
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), 5 avenue des Hauts-Fourneaux, L-4362 Esch/Alzette, Luxemburg
- Department of Physics and Materials Science, University of Luxembourg, Rue du Brill 41, L-4422 Belvaux, Luxembourg
| | - Pablo García-Fernández
- Departmento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, 39005 Santander, Spain
| | - Javier Junquera
- Departmento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, 39005 Santander, Spain
| | - Stephen W Lovesey
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Department of Physics, Oxford University, Oxford OX1 3PU, United Kingdom
| | - Gerrit van der Laan
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Se Young Park
- Department of Physics, Soongsil University, Seoul 06978, Korea
| | - John W Freeland
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Lane W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Dong Ryeol Lee
- Department of Physics, Soongsil University, Seoul 06978, Korea
| | - Ramamoorthy Ramesh
- Department of Physics, University of California, Berkeley, California 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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