1
|
Damodaran AR, Clarkson JD, Hong Z, Liu H, Yadav AK, Nelson CT, Hsu SL, McCarter MR, Park KD, Kravtsov V, Farhan A, Dong Y, Cai Z, Zhou H, Aguado-Puente P, García-Fernández P, Íñiguez J, Junquera J, Scholl A, Raschke MB, Chen LQ, Fong DD, Ramesh R, Martin LW. Phase coexistence and electric-field control of toroidal order in oxide superlattices. Nat Mater 2017; 16:1003-1009. [PMID: 28783161 DOI: 10.1038/nmat4951] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 06/28/2017] [Indexed: 06/07/2023]
Abstract
Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO3/SrTiO3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a1/a2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities.
Collapse
Affiliation(s)
- A R Damodaran
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - J D Clarkson
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Z Hong
- Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16802, USA
| | - H Liu
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - A K Yadav
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- School of Electrical Engineering and Computer Science, UC Berkeley, Berkeley, California 94720, USA
| | - C T Nelson
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S-L Hsu
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - M R McCarter
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, USA
| | - K-D Park
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Boulder, Colorado 80309, USA
| | - V Kravtsov
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Boulder, Colorado 80309, USA
| | - A Farhan
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Y Dong
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Z Cai
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - H Zhou
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - P Aguado-Puente
- Centro de Física de Materiales, Universidad del País Vasco, 20018 San Sebastián, Spain
- Donostia International Physics Center, 20018 San Sebastián, Spain
| | - P García-Fernández
- Departmento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, avenida de los Castros s/n, 39005 Santander, Spain
| | - J Íñiguez
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), 5 avenue des Hauts-Fourneaux, L-4362 Esch/Alzette, Luxembourg
| | - J Junquera
- Departmento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, avenida de los Castros s/n, 39005 Santander, Spain
| | - A Scholl
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - M B Raschke
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Boulder, Colorado 80309, USA
| | - L-Q Chen
- Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16802, USA
| | - D D Fong
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - R Ramesh
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, USA
| | - L 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
| |
Collapse
|
2
|
Abstract
The goal of antenna design at optical frequencies is to deliver optical electromagnetic energy to loads in the form of, e.g., atoms, molecules or nanostructures, or to enhance the radiative emission from such structures, or both. A true optical antenna would, on a qualitatively new level, control the light-matter interaction on the nanoscale for controlled optical signal transduction, radiative decay engineering, quantum coherent control, and super-resolution microscopy, and provide unprecedented sensitivity in spectroscopy. Resonant metallic structures have successfully been designed to approach these goals. They are called optical antennas in analogy to radiofrequency (RF) antennas due to their capability to collect and control electromagnetic fields at optical frequencies. However, in contrast to the RF, where exact design rules for antennas, waveguides, and antenna-load matching in terms of their impedances are well established, substantial physical differences limit the simple extension of the RF concepts into the optical regime. Key distinctions include, for one, intrinsic material resonances including quantum state excitations (metals, metal oxides, semiconductor homo- and heterostructures) and extrinsic resonances (surface plasmon/phonon polaritons) at optical frequencies. Second, in the absence of discrete inductors, capacitors, and resistors, new design strategies must be developed to impedance match the antenna to the load, ultimately in the form of a vibrational, electronic, or spin excitation on the quantum level. Third, there is as yet a lack of standard performance metrics for characterizing, comparing and quantifying optical antenna performance. Therefore, optical antenna development is currently challenged at all the levels of design, fabrication, and characterization. Here we generalize the ideal antenna-load interaction at optical frequencies, characterized by three main steps: (i) far-field reception of a propagating mode exciting an antenna resonance, (ii) subsequent transformation of that mode into a nanoscale spatial localization, and (iii) near-field coupling via an enhanced local density of states to a quantum load. These three steps define the goal of efficient transformation of incident radiation into a quantum excitation in an impedance-matched fashion. We review the physical basis of the light-matter interaction at the transition from the RF to optical regime, discuss the extension of antenna theory as needed for the design of impedance-matched optical antenna-load coupled systems, and provide several examples of the state of the art in design strategies and suggest future extensions. We furthermore suggest new performance metrics based on the combination of electric vector field, field enhancement and capture cross section measurement to aid in comparison between different antenna designs and optimization of optical antenna performance within the physical parameter space.
Collapse
Affiliation(s)
- R L Olmon
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, CO 80309, USA
| | | |
Collapse
|