Observation of room temperature polar skyrmions

Invited

Abstract

Complex topological configurations are a fertile playground to explore novel emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polarization vortices and the associated complex-phase coexistence and response under applied field in superlattices of (PbTiO3)n/(SrTiO3)n suggests the presence of a complex, multi-dimensional system capable of exotic physical responses. I will describe the discovery of polar skyrmions in a lead-titanate layer confined by strontium-titanate layers by atomic-resolution scanning transmission electron microscopy (STEM). Phase-field modeling and second-principles calculations reveal that the polar skyrmions have a skyrmion number of +1 and resonant soft X-ray diffraction experiments show circular dichroism confirming chirality. Such nanometer-scale polar skyrmions exhibit a strong signature of negative permittivity at the surface of the skyrmion, which is furthermore highly tunable with an electric field. They are a new state of matter and electric analogs of magnetic skyrmions, and may be envisaged for potential applications in information technologies. I will attempt to describe the exciting observations we have made through many collaborations.

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Presenters

  • Ramamoorthy Ramesh

    Department of Materials Science and Engineering, UC Berkeley, University of California, Berkeley, USA, University of California, Berkeley, Materials Science and Engineering, University of California, Berkeley, Department of Materials Science and Engineering, University of California, Berkeley, Department of Materials Science and Engineering,, University of California, Berkeley, California 94720, USA

Authors

  • Ramamoorthy Ramesh

    Department of Materials Science and Engineering, UC Berkeley, University of California, Berkeley, USA, University of California, Berkeley, Materials Science and Engineering, University of California, Berkeley, Department of Materials Science and Engineering, University of California, Berkeley, Department of Materials Science and Engineering,, University of California, Berkeley, California 94720, USA