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Polar-vortex-driven interfacial strain coupling in PbTiO3/SrRuO3 Heterostructures
Authors:
S. A. Raza,
V. A. Stoica,
H. Zheng,
H. G. Lee,
A. Ross,
U. Saha,
L. Q. Chen,
L. W. Martin,
V. Gopalan,
J. W. Freeland
Abstract:
Interfacial coupling in oxide heterostructures is a central problem in condensed-matter physics, as it typically emerges at the atomic scale through local interactions mediated by lattice polarization and strain. In this work, we investigate nanoscale polar-supertexture-driven interfacial strain coupling in (PbTiO3)16/(SrRuO3)9/(PbTiO3)16 heterostructures grown on DyScO3(110) substrates. Under app…
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Interfacial coupling in oxide heterostructures is a central problem in condensed-matter physics, as it typically emerges at the atomic scale through local interactions mediated by lattice polarization and strain. In this work, we investigate nanoscale polar-supertexture-driven interfacial strain coupling in (PbTiO3)16/(SrRuO3)9/(PbTiO3)16 heterostructures grown on DyScO3(110) substrates. Under appropriate epitaxial strain conditions, the PbTiO3 layers form polar vortex superstructures with a periodicity of approximately 10 nm. We demonstrate that the resulting in-plane nanoscale strain modulation propagates into the SrRuO3 layer. Using element-specific resonant X-ray reflectivity, we probe the nanoscale strain modulations of the strontium and ruthenium sublattices at the interface, revealing strong interfacial strain coupling between the ferroelectric and ferromagnetic layers. These findings provide new insights into engineering nanoscale magnetic modulations through interfacial strain and polarization control.
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Submitted 10 August, 2026;
originally announced August 2026.
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Above Room Temperature Ferroelectricity in Epitaxially Strained KTaO3
Authors:
Tobias Schwaigert,
Salva Salmani-Rezaie,
Sankalpa Hazra,
Utkarsh Saha,
Maya Ramesh,
Aiden Ross,
Betul Pamuk,
Long-Qing Chen,
David A. Muller,
Darrell G. Schlom,
Venkatraman Gopalan,
Kaveh Ahadi
Abstract:
Epitaxial strain is a powerful means to engineer emergent phenomena in thin films and heterostructures. Here, we demonstrate that KTaO3, a cubic perovskite in bulk form, can be epitaxially strained into a highly tunable ferroelectric. KTaO3 films grown commensurate to SrTiO3 (001) substrates experience an in-plane strain of -2.1 % that transforms the cubic structure into a tetragonal polar phase w…
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Epitaxial strain is a powerful means to engineer emergent phenomena in thin films and heterostructures. Here, we demonstrate that KTaO3, a cubic perovskite in bulk form, can be epitaxially strained into a highly tunable ferroelectric. KTaO3 films grown commensurate to SrTiO3 (001) substrates experience an in-plane strain of -2.1 % that transforms the cubic structure into a tetragonal polar phase with transition temperature of 475 K, consistent with our thermodynamic calculations. We show that the Curie temperature and the spontaneous electric polarization can be system- atically controlled with epitaxial strain. Scanning transmission electron microscopy reveals cooperative polar displacements of the potassium columns with respect to the neighboring tantalum columns at room temperature. Optical second-harmonic generation results are described by a tetragonal polar point group (4mm), indicating the emergence of a global polar ground state. We observe a ferroelectric hysteresis response, using metal-insulator-metal capacitor test structures. The results demon- strate a robust intrinsic ferroelectric state in epitaxially strained KTaO3 thin films.
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Submitted 22 January, 2026; v1 submitted 20 January, 2026;
originally announced January 2026.
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Terahertz-field activation of polar skyrons
Authors:
Huaiyu Wang,
Vladimir Stoica,
Cheng Dai,
Marek Paściak,
Sujit Das,
Tiannan Yang,
Mauro A. P. Gonçalves,
Jiri Kulda,
Margaret R. McCarter,
Anudeep Mangu,
Yue Cao,
Hari Padma,
Utkarsh Saha,
Diling Zhu,
Takahiro Sato,
Sanghoon Song,
Mathias Hoffmann,
Patrick Kramer,
Silke Nelson,
Yanwen Sun,
Quynh Nguyen,
Zhan Zhang,
Ramamoorthy Ramesh,
Lane Martin,
Aaron M. Lindenberg
, et al. (5 additional authors not shown)
Abstract:
Unraveling collective modes arising from coupled degrees of freedom is crucial for understanding complex interactions in solids and developing new functionalities. Unique collective behaviors emerge when two degrees of freedom, ordered on distinct length scales, interact. Polar skyrmions, three-dimensional electric polarization textures in ferroelectric superlattices, disrupt the lattice continuit…
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Unraveling collective modes arising from coupled degrees of freedom is crucial for understanding complex interactions in solids and developing new functionalities. Unique collective behaviors emerge when two degrees of freedom, ordered on distinct length scales, interact. Polar skyrmions, three-dimensional electric polarization textures in ferroelectric superlattices, disrupt the lattice continuity at the nanometer scale with nontrivial topology, leading to previously unexplored collective modes. Here, using terahertz-field excitation and femtosecond x-ray diffraction, we discovered subterahertz collective modes, dubbed 'skyrons', which appear as swirling patterns of atomic displacements functioning as atomic-scale gearsets. Momentum-resolved time-domain measurements of diffuse scattering revealed an avoided crossing in the dispersion relation of skyrons. We further demonstrated that the amplitude and dispersion of skyrons can be controlled by sample temperature and electric-field bias. Atomistic simulations and dynamical phase-field modeling provided microscopic insights into the three-dimensional crystallographic and polarization dynamics. The discovery of skyrons and their coupling with terahertz fields opens avenues for ultrafast control of topological polar structures.
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Submitted 1 September, 2025; v1 submitted 15 May, 2025;
originally announced May 2025.
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Screening of potential double perovskite materials for photovoltaic applications using agglomerative hierarchical clustering
Authors:
Utkarsh Saha,
Koyendrila Debnath,
Soumitra Satapathi
Abstract:
Data-driven approaches to solve problems in materials science have gained immense popularity in recent times due to their ability to predict unknown material properties and uncover relationships between structure and property. Machine learning algorithms like GBRT, random forest and neural networks have had tremendous success in predicting target properties of materials and design of structures fo…
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Data-driven approaches to solve problems in materials science have gained immense popularity in recent times due to their ability to predict unknown material properties and uncover relationships between structure and property. Machine learning algorithms like GBRT, random forest and neural networks have had tremendous success in predicting target properties of materials and design of structures for various applications. However, a major drawback for achieving results within the required accuracy using these algorithms has been the need for large datasets which can be challenging for problems when data is not sufficiently available for training the models. In this work, we propose the use of a hierarchical clustering algorithm which can work considerably better on materials science problems with small dataset constraints. We apply the algorithm to screen out promising double perovskite materials as candidates for solar cells.
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Submitted 15 November, 2021;
originally announced November 2021.
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An atomic frequency comb memory in rare-earth doped thin-film lithium niobate
Authors:
Subhojit Dutta,
Yuqi Zhao,
Uday Saha,
Demitry Farfurnik,
Elizabeth A. Goldschmidt,
Edo Waks
Abstract:
Atomic frequency combs memories that coherently store optical signals are a key building block for optical quantum computers and quantum networks. Integrating such memories into compact and chip-scale devices is essential for scalable quantum technology, but to date most demonstrations have been in bulk materials or waveguides with large cross-sections, or using fabrication techniques not easily a…
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Atomic frequency combs memories that coherently store optical signals are a key building block for optical quantum computers and quantum networks. Integrating such memories into compact and chip-scale devices is essential for scalable quantum technology, but to date most demonstrations have been in bulk materials or waveguides with large cross-sections, or using fabrication techniques not easily adaptable to wafer scale processing. We demonstrate compact chip-integrated atomic frequency comb storage in rare earth doped thin-film lithium niobate. Our optical memory exhibits a broad storage bandwidth exceeding 100 MHz, and optical storage time of over 250 ns. The enhanced optical confinement in this device structure enables three orders of magnitude reduction in optical power as compared to large ion-diffused waveguides for the same Rabi frequency. These compact atomic frequency comb memories pave the way towards scalable, highly efficient, electro-optically tunable quantum photonic systems that can store and manipulate light on a compact chip.
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Submitted 22 November, 2021; v1 submitted 2 November, 2021;
originally announced November 2021.
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An Integrated Photonic Platform for Rare-Earth Ions in Thin Film Lithium Niobate
Authors:
Subhojit Dutta,
Elizabeth A. Goldschmidt,
Sabyasachi Barik,
Uday Saha,
Edo Waks
Abstract:
Rare-earth ion ensembles doped in single crystals are a promising materials system with widespread applications in optical signal processing, lasing, and quantum information processing. Incorporating rare-earth ions into integrated photonic devices could enable compact lasers and modulators, as well as on-chip optical quantum memories for classical and quantum optical applications. To this end, a…
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Rare-earth ion ensembles doped in single crystals are a promising materials system with widespread applications in optical signal processing, lasing, and quantum information processing. Incorporating rare-earth ions into integrated photonic devices could enable compact lasers and modulators, as well as on-chip optical quantum memories for classical and quantum optical applications. To this end, a thin film single crystalline wafer structure that is compatible with planar fabrication of integrated photonic devices would be highly desirable. However, incorporating rare-earth ions into a thin film form-factor while preserving their optical properties has proven challenging. We demonstrate an integrated photonic platform for rare-earth ions doped in a single crystalline thin film on insulator. The thin film is composed of lithium niobate doped with Tm3+. The ions in the thin film exhibit optical lifetimes identical to those measured in bulk crystals. We show narrow spectral holes in a thin film waveguide that require up to 2 orders of magnitude lower power to generate than previously reported bulk waveguides. Our results pave way for scalable on-chip lasers, optical signal processing devices, and integrated optical quantum memories.
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Submitted 14 November, 2019;
originally announced November 2019.