TY - JOUR
T1 - Author Correction: Spatially resolved steady-state negative capacitance (Nature, (2019), 565, 7740, (468-471), 10.1038/s41586-018-0855-y)
JF - Nature
Y1 - 2019/
SP - E13
A1 - A.K. Yadav
A1 - K.X. Nguyen
A1 - Z. Hong
A1 - P. García-Fernández
A1 - P. Aguado-Puente
A1 - C.T. Nelson
A1 - S. Das
A1 - B. Prasad
A1 - D. Kwon
A1 - S. Cheema
A1 - A.I. Khan
A1 - C. Hu
A1 - J. Íñiguez
A1 - J. Junquera
A1 - L.-Q. Chen
A1 - D.A. Muller
A1 - Ramamoorthy Ramesh
A1 - S. Salahuddin
KW - erratum
KW - error
AB - In this Letter, the first name of author Bhagwati Prasad was misspelled Bhagawati. This error has been corrected online. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
PB - Nature Publishing Group
VL - 568
N1 - cited By 0
ER -
TY - JOUR
T1 - Emergence of the Vortex State in Confined Ferroelectric Heterostructures
JF - Advanced Materials
Y1 - 2019/
A1 - S.-L. Hsu
A1 - M.R. McCarter
A1 - C. Dai
A1 - Z. Hong
A1 - L.-Q. Chen
A1 - C.T. Nelson
A1 - L.W. Martin
A1 - Ramamoorthy Ramesh
KW - Degrees of freedom (mechanics)
KW - Ferroelectric state
KW - Ferroelectric superlattice
KW - ferroelectricity
KW - High resolution transmission electron microscopy
KW - Interface states
KW - Lead titanate
KW - Long range interactions
KW - Memory applications
KW - Number of unit cells
KW - Phase field models
KW - phase transitions
KW - Polar structures
KW - Strontium titanates
KW - titanium compounds
KW - Vortex flow
KW - Vortex state
AB - The manipulation of charge and lattice degrees of freedom in atomically precise, low-dimensional ferroelectric superlattices can lead to exotic polar structures, such as a vortex state. The role of interfaces in the evolution of the vortex state in these superlattices (and the associated electrostatic and elastic boundary conditions they produce) has remained unclear. Here, the toroidal state, arranged in arrays of alternating clockwise/counterclockwise polar vortices, in a confined SrTiO3/PbTiO3/SrTiO3 trilayer is investigated. By utilizing a combination of transmission electron microscopy, synchrotron-based X-ray diffraction, and phase-field modeling, the phase transition as a function of layer thickness (number of unit cells) demonstrates how the vortex state emerges from the ferroelectric state by varying the thickness of the confined PbTiO3 layer. Intriguingly, the vortex state arises at head-to-head domain boundaries in ferroelectric a1/a2 twin structures. In turn, by varying the total number of PbTiO3 layers (moving from trilayer to superlattices), it is possible to manipulate the long-range interactions among multiple confined PbTiO3 layers to stabilize the vortex state. This work provides a new understanding of how the different energies work together to produce this exciting new state of matter and can contribute to the design of novel states and potential memory applications. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PB - Wiley-VCH Verlag
VL - 31
N1 - cited By 2
ER -
TY - JOUR
T1 - Observation of room-temperature polar skyrmions
JF - Nature
Y1 - 2019/
SP - 368
EP - 372
A1 - S. Das
A1 - Y.L. Tang
A1 - Z. Hong
A1 - M.A.P. Gonçalves
A1 - M.R. McCarter
A1 - C. Klewe
A1 - K.X. Nguyen
A1 - F. Gómez-Ortiz
A1 - P. Shafer
A1 - E. Arenholz
A1 - V.A. Stoica
A1 - S.-L. Hsu
A1 - B. Wang
A1 - C. Ophus
A1 - J.F. Liu
A1 - C.T. Nelson
A1 - S. Saremi
A1 - B. Prasad
A1 - A.B. Mei
A1 - D.G. Schlom
A1 - J. Íñiguez
A1 - P. García-Fernández
A1 - D.A. Muller
A1 - L.Q. Chen
A1 - J. Junquera
A1 - L.W. Martin
A1 - Ramamoorthy Ramesh
KW - chirality
KW - circular dichroism
KW - electric activity
KW - electric capacitance
KW - electric field
KW - electromagnetism
KW - Letter
KW - Magnetism
KW - Polarization
KW - priority journal
KW - room temperature
KW - scanning transmission electron microscopy
KW - titanium
KW - transmission electron microscopy
KW - X ray diffraction
AB - Complex topological configurations are fertile ground for exploring emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polarization vortices and their associated complex-phase coexistence and response under applied electric fields in superlattices of (PbTiO3)n/(SrTiO3)n suggests the presence of a complex, multi-dimensional system capable of interesting physical responses, such as chirality, negative capacitance and large piezo-electric responses1–3. Here, by varying epitaxial constraints, we discover room-temperature polar-skyrmion bubbles in a lead titanate layer confined by strontium titanate layers, which are imaged by atomic-resolution scanning transmission electron microscopy. Phase-field modelling and second-principles calculations reveal that the polar-skyrmion bubbles have a skyrmion number of +1, and resonant soft-X-ray diffraction experiments show circular dichroism, confirming chirality. Such nanometre-scale polar-skyrmion bubbles are the electric analogues of magnetic skyrmions, and could contribute to the advancement of ferroelectrics towards functionalities incorporating emergent chirality and electrically controllable negative capacitance. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
PB - Nature Publishing Group
VL - 568
N1 - cited By 31
ER -
TY - JOUR
T1 - Optical creation of a supercrystal with three-dimensional nanoscale periodicity
JF - Nature Materials
Y1 - 2019/
SP - 377
EP - 383
A1 - V.A. Stoica
A1 - N. Laanait
A1 - C. Dai
A1 - Z. Hong
A1 - Y. Yuan
A1 - Z. Zhang
A1 - S. Lei
A1 - M.R. McCarter
A1 - A. Yadav
A1 - A.R. Damodaran
A1 - S. Das
A1 - G.A. Stone
A1 - J. Karapetrova
A1 - D.A. Walko
A1 - X. Zhang
A1 - L.W. Martin
A1 - Ramamoorthy Ramesh
A1 - L.-Q. Chen
A1 - H. Wen
A1 - V. Gopalan
A1 - J.W. Freeland
KW - Coherent scattering
KW - Dielectric properties
KW - Lead titanate
KW - light
KW - Magnetic phenomena
KW - Nano-scale periodicity
KW - Non-equilibrium phasis
KW - Phase field models
KW - Photo-induced charge
KW - Three-dimensional structure
KW - Two phase flow
KW - Two-phase equilibria
KW - Ultrafast light pulse
KW - X ray scattering
AB - Stimulation with ultrafast light pulses can realize and manipulate states of matter with emergent structural, electronic and magnetic phenomena. However, these non-equilibrium phases are often transient and the challenge is to stabilize them as persistent states. Here, we show that atomic-scale PbTiO 3 /SrTiO 3 superlattices, counterpoising strain and polarization states in alternate layers, are converted by sub-picosecond optical pulses to a supercrystal phase. This phase persists indefinitely under ambient conditions, has not been created via equilibrium routes, and can be erased by heating. X-ray scattering and microscopy show this unusual phase consists of a coherent three-dimensional structure with polar, strain and charge-ordering periodicities of up to 30 nm. By adjusting only dielectric properties, the phase-field model describes this emergent phase as a photo-induced charge-stabilized supercrystal formed from a two-phase equilibrium state. Our results demonstrate opportunities for light-activated pathways to thermally inaccessible and emergent metastable states. © 2019, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.
PB - Nature Publishing Group
VL - 18
N1 - cited By 9
ER -
TY - JOUR
T1 - Spatially resolved steady-state negative capacitance
JF - Nature
Y1 - 2019/
SP - 468
EP - 471
A1 - A.K. Yadav
A1 - K.X. Nguyen
A1 - Z. Hong
A1 - P. García-Fernández
A1 - P. Aguado-Puente
A1 - C.T. Nelson
A1 - S. Das
A1 - B. Prasad
A1 - D. Kwon
A1 - S. Cheema
A1 - A.I. Khan
A1 - C. Hu
A1 - J. Íñiguez
A1 - J. Junquera
A1 - L.-Q. Chen
A1 - D.A. Muller
A1 - Ramamoorthy Ramesh
A1 - S. Salahuddin
KW - chemical structure
KW - electric capacitance
KW - electric field
KW - electrical parameters
KW - energy density
KW - ferroelectric dielectric heterostructure
KW - Letter
KW - negative capacitance
KW - Polarization
KW - priority journal
KW - scanning transmission electron microscopy
KW - simulation
KW - steady state
KW - X ray diffraction
AB - Negative capacitance is a newly discovered state of ferroelectric materials that holds promise for electronics applications by exploiting a region of thermodynamic space that is normally not accessible1–14. Although existing reports of negative capacitance substantiate the importance of this phenomenon, they have focused on its macroscale manifestation. These manifestations demonstrate possible uses of steady-state negative capacitance—for example, enhancing the capacitance of a ferroelectric–dielectric heterostructure4,7,14 or improving the subthreshold swing of a transistor8–12. Yet they constitute only indirect measurements of the local state of negative capacitance in which the ferroelectric resides. Spatial mapping of this phenomenon would help its understanding at a microscopic scale and also help to achieve optimal design of devices with potential technological applications. Here we demonstrate a direct measurement of steady-state negative capacitance in a ferroelectric–dielectric heterostructure. We use electron microscopy complemented by phase-field and first-principles-based (second-principles) simulations in SrTiO3/PbTiO3 superlattices to directly determine, with atomic resolution, the local regions in the ferroelectric material where a state of negative capacitance is stabilized. Simultaneous vector mapping of atomic displacements (related to a complex pattern in the polarization field), in conjunction with reconstruction of the local electric field, identify the negative capacitance regions as those with higher energy density and larger polarizability: the domain walls where the polarization is suppressed. © 2019, Springer Nature Limited.
PB - Nature Publishing Group
VL - 565
N1 - cited By 35
ER -
TY - JOUR
T1 - Phase coexistence and electric-field control of toroidal order in oxide superlattices
JF - Nature Materials
Y1 - 2017/
SP - 1003
EP - 1009
A1 - A.R. Damodaran
A1 - J.D. Clarkson
A1 - Z. Hong
A1 - H. B. Liu
A1 - A.K. Yadav
A1 - C.T. Nelson
A1 - S.-L. Hsu
A1 - M.R. McCarter
A1 - K.-D. Park
A1 - V. Kravtsov
A1 - A. Farhan
A1 - Y. Dong
A1 - Z. Cai
A1 - H. Zhou
A1 - P. Aguado-Puente
A1 - P. García-Fernández
A1 - J. Íñiguez
A1 - J. Junquera
A1 - A. Scholl
A1 - M.B. Raschke
A1 - L.-Q. Chen
A1 - D.D. Fong
A1 - Ramamoorthy Ramesh
A1 - L.W. Martin
KW - Characterization techniques
KW - Condensed matter physics
KW - Electric fields
KW - Electric-field control
KW - Ferroelectric domains
KW - Ferroelectric phasis
KW - ferroelectricity
KW - First-order phase transitions
KW - Nonlinear optical response
KW - Oxide superlattices
KW - Polarization
KW - Superlattice periods
KW - temperature
KW - Vortex flow
AB - 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 PbTiO"3/SrTiO"3 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 a"1/a"2 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. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
PB - Nature Publishing Group
VL - 16
N1 - cited By 50
ER -
TY - JOUR
T1 - Stability of Polar Vortex Lattice in Ferroelectric Superlattices
JF - Nano Letters
Y1 - 2017/
SP - 2246
EP - 2252
A1 - Z. Hong
A1 - A.R. Damodaran
A1 - F. Xue
A1 - S.-L. Hsu
A1 - J. Britson
A1 - A.K. Yadav
A1 - C.T. Nelson
A1 - J.-J. Wang
A1 - J.F. Scott
A1 - L.W. Martin
A1 - Ramamoorthy Ramesh
A1 - L.-Q. Chen
KW - Article
KW - competition
KW - Crystal lattices
KW - Ferroelectric superlattice
KW - ferroelectricity
KW - Geometric length
KW - Neodymium compounds
KW - Phase-field simulation
KW - Polar vortex
KW - Polarization
KW - simulation
KW - Superconducting materials
KW - Topological structure
KW - Topology
KW - Vortex flow
AB - A novel mesoscale state comprising of an ordered polar vortex lattice has been demonstrated in ferroelectric superlattices of PbTiO3/SrTiO3. Here, we employ phase-field simulations, analytical theory, and experimental observations to evaluate thermodynamic conditions and geometric length scales that are critical for the formation of such exotic vortex states. We show that the stability of these vortex lattices involves an intimate competition between long-range electrostatic, long-range elastic, and short-range polarization gradient-related interactions leading to both an upper and a lower bound to the length scale at which these states can be observed. We found that the critical length is related to the intrinsic domain wall width, which could serve as a simple intuitive design rule for the discovery of novel ultrafine topological structures in ferroic systems. © 2017 American Chemical Society.
PB - American Chemical Society
VL - 17
N1 - cited By 36
ER -
TY - JOUR
T1 - Erratum: Observation of polar vortices in oxide superlattices (Nature (2016) 530 (198-201) DOI:10.1038/nature16463)
JF - Nature
Y1 - 2016/
SP - 138
A1 - A.K. Yadav
A1 - C.T. Nelson
A1 - S.L. Hsu
A1 - Z. Hong
A1 - J.D. Clarkson
A1 - C.M. Schlepütz
A1 - A.R. Damodaran
A1 - P. Shafer
A1 - E. Arenholz
A1 - L.R. Dedon
A1 - D. Chen
A1 - A. Vishwanath
A1 - A.M. Minor
A1 - L.Q. Chen
A1 - J.F. Scott
A1 - L.W. Martin
A1 - Ramamoorthy Ramesh
KW - erratum
KW - error
PB - Nature Publishing Group
VL - 534
N1 - cited By 3
ER -
TY - JOUR
T1 - Observation of polar vortices in oxide superlattices
JF - Nature
Y1 - 2016/
SP - 198
EP - 201
A1 - A.K. Yadav
A1 - C.T. Nelson
A1 - S.L. Hsu
A1 - Z. Hong
A1 - J.D. Clarkson
A1 - C.M. Schlepuëtz
A1 - A.R. Damodaran
A1 - P. Shafer
A1 - E. Arenholz
A1 - L.R. Dedon
A1 - D. Chen
A1 - A. Vishwanath
A1 - A.M. Minor
A1 - L.Q. Chen
A1 - J.F. Scott
A1 - L.W. Martin
A1 - Ramamoorthy Ramesh
KW - Erinaceidae
AB - The complex interplay of spin, charge, orbital and lattice degrees of freedom provides a plethora of exotic phases and physical phenomena. In recent years, complex spin topologies have emerged as a consequence of the electronic band structure and the interplay between spin and spin-orbit coupling in materials. Here we produce complex topologies of electrical polarization-namely, nanometre-scale vortex-antivortex (that is, clockwise-anticlockwise) arrays that are reminiscent of rotational spin topologies-by making use of the competition between charge, orbital and lattice degrees of freedom in superlattices of alternating lead titanate and strontium titanate layers. Atomic-scale mapping of the polar atomic displacements by scanning transmission electron microscopy reveals the presence of long-range ordered vortex-antivortex arrays that exhibit nearly continuous polarization rotation. Phase-field modelling confirms that the vortex array is the low-energy state for a range of superlattice periods. Within this range, the large gradient energy from the vortex structure is counterbalanced by the corresponding large reduction in overall electrostatic energy (which would otherwise arise from polar discontinuities at the lead titanate/strontium titanate interfaces) and the elastic energy associated with epitaxial constraints and domain formation. These observations have implications for the creation of new states of matter (such as dipolar skyrmions, hedgehog states) and associated phenomena in ferroic materials, such as electrically controllable chirality. © 2016 Macmillan Publishers Limited. All rights reserved.
PB - Nature Publishing Group
VL - 530
N1 - cited By 248
ER -