A5072321450- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
- Advanced Condensed Matter Physics
- Ferroelectric and Piezoelectric Materials
- Physics of Superconductivity and Magnetism
- Semiconductor materials and devices
- Magnetic properties of thin films
- Catalytic Processes in Materials Science
- Spectroscopy and Laser Applications
- Surface and Thin Film Phenomena
- Iron-based superconductors research
- Terahertz technology and applications
- Acoustic Wave Resonator Technologies
- Rare-earth and actinide compounds
- Photorefractive and Nonlinear Optics
- Inorganic Chemistry and Materials
- Topological Materials and Phenomena
- Solidification and crystal growth phenomena
- 2D Materials and Applications
- Semiconductor Quantum Structures and Devices
- Metallurgical and Alloy Processes
- Advanced Materials Characterization Techniques
- Chemical Thermodynamics and Molecular Structure
- Advanced ceramic materials synthesis
- Smart Materials for Construction
Cornell University
2010-2024
Max Planck Institute for the Structure and Dynamics of Matter
2017-2024
Center for Free-Electron Laser Science
2020
Universität Hamburg
2020
Hamburg Centre for Ultrafast Imaging
2020
Yale University
2013-2019
Interface (United States)
2013-2017
Korea Foundation for Max Planck POSTECH
2017
Driving strontium titanate ferroelectric Hidden phases are metastable collective states of matter that typically not accessible on equilibrium phase diagrams. Nova et al. used infrared pulses to excite higher-frequency lattice modes drive the crystal into a phase, can persist for many hours. X. Li terahertz fields soft mode moves ions in positions they occupy new phase. The this case was transient, lasting order 10 picoseconds. Because these hidden host exotic properties otherwise...
Abstract In quantum materials, degeneracies and frustrated interactions can have a profound impact on the emergence of long-range order, often driving strong fluctuations that suppress functionally relevant electronic or magnetic phases 1–7 . Engineering atomic structure in bulk at heterointerfaces has been an important research strategy to lift these degeneracies, but equilibrium methods are limited by thermodynamic, elastic chemical constraints 8 Here we show all-optical, mode-selective...
Abstract Crystal lattice fluctuations, which are known to influence phase transitions of quantum materials in equilibrium, also expected determine the dynamics light-induced changes. However, they have only rarely been explored these dynamical settings. Here we study time evolution fluctuations paraelectric SrTiO 3 , mid-infrared drives shown induce a metastable ferroelectric state. Crucial physics is competition between polar instabilities and antiferrodistortive rotations, equilibrium...
We experimentally demonstrate a novel approach to substantially modify orbital occupations and symmetries in electronically correlated oxides. In contrast methods using strain or confinement, this tuning is achieved by exploiting charge transfer inversion symmetry breaking atomically layered heterostructures. illustrate the technique LaTiO3−LaNiO3−LaAlO3 system; combination of x-ray absorption spectroscopy ab initio theory reveals electron concomitant polar fields, resulting ∼50% change...
Metallic electronic transport in nickelate heterostructures can be induced and confined to two dimensions (2D) by controlling the structural parameters of nickel–oxygen planes.
We describe a general materials design approach that produces large orbital energy splittings (orbital polarization) in nickelate heterostructures, creating two-dimensional single-band electronic surface at the Fermi energy. The resulting structure mimics of high temperature cuprate superconductors. two key ingredients are: (i) construction atomic-scale distortions about Ni site via charge transfer and internal electric fields, (ii) use three component (tri-component) superlattices to break...
SnTe is a topological crystalline insulator that possesses spin-polarized, Dirac-dispersive surface states protected by crystal symmetry. Multiple exist on the {100}, {110}, and {111} surfaces of SnTe, with band structure depending mirror symmetry particular surface. Thus, to access selectively, it critical control morphology such only desired crystallographic are present. Here, we grow nanostructures using vapor-liquid-solid vapor-solid growth mechanisms. Previously, nanowires nanocrystals...
Tailoring the microscopic structures of oxide interfaces and surfaces to realize desired electronic properties is intense interest. The authors modulate conductivity LaNiO${}_{3}$ films as thin three unit cells by precisely controlling composition topmost atomic layer. Three-dimensional x-ray imaging combined with first-principles theory exposes correlation between surface termination electrical conductivity, which could be widely exploited in logic, memory, or sensor applications.
A new and surprising property is discovered when a ferroelectric nonvolatile gate combined with conductive oxide channel: When the polarization switched, single atomic layer in normally insulating becomes conductive. This has high mobility dominant channel all-oxide heterostructure. approach can be extended to control properties of any at interface between material, presents qualitative shift our understanding field effect.
The complex phase diagrams of strongly correlated oxides arise from the coupling between physical and electronic structure. This can lead to a renormalization boundaries when considering thin films rather than bulk crystals due reduced dimensionality epitaxial strain. well-established RNiO3 diagram shows systematic dependence metal-insulator transition perovskite A-site rare-earth ion, R. Here, we explore equivalent for nickelate under compressive We determine solid solution Nd1-yLayNiO3...
In complex oxide materials, changes in electronic properties are often associated with crystal structure, raising the question of relative roles and lattice effects driving metal-insulator transition. This paper presents a combined theoretical experimental analysis dependence transition [Formula: see text] on specifically comparing bulk materials to 1- 2-layer samples grown between multiple electronically inert counterlayers superlattice. The comparison amplifies validates approach developed...
Abstract In crystalline materials, the presence of surfaces or interfaces gives rise to crystal truncation rods (CTRs) in their X‐ray diffraction patterns. While structural properties related bulk a are contained intensity and position Bragg peaks diffraction, CTRs carry detailed information about atomic structure at interface. Developments synchrotron sources, instrumentation, analysis procedures have made CTR measurements into extremely powerful tools study reconstructions relaxations...
The relative energies and occupancies of valence orbital states can dramatically influence collective electronic magnetic phenomena in correlated transition metal oxide systems. We review the current state research on modification control these properties rare-earth nickelates, especially LaNiO3, a model degenerate d system where significant recent progress has been made. Theoretical experimental results thin films heterostructures are described, including correlation effects. highlight...
Resonant inelastic x-ray scattering is used to investigate the electronic origin of orbital polarization in nickelate heterostructures taking $\mathrm{LaTiO_3-LaNiO_3-3x(LaAlO_3)}$, a system with exceptionally large polarization, as model system. We find that heterostructuring generates only minor changes Ni $3d$ energy levels, contradicting often-invoked picture which levels generate polarization. Instead, O $K$-edge absorption spectroscopy demonstrates caused by an anisotropic...
Recently, two-dimensional terahertz spectroscopy (2DTS) has attracted increasing attention for studying complex solids. A number of recent studies have applied 2DTS either with long pulses or away from any material resonances, situations that yield unconventional spectra are often difficult to interpret. Here, we clarify the generic origins observed spectral features by examining ZnTe, a model system featureless optical susceptibility at low frequencies. These results also reveal possible...
Electronic, lattice, and spin interactions at the interfaces between crystalline complex transition metal oxides can give rise to a wide range of functional electronic magnetic phenomena not found in bulk. At hetero-interfaces, these may be enhanced by combining where polarity changes interface. The physical structure non-polar SrTiO$_3$ polar La$_{1-x}$Sr$_x$MnO$_3$(x=0.2) is investigated using high resolution synchrotron x-ray diffraction directly determine role compensating discontinuity....
Coherent and epitaxial interfaces permit the realization of electric field driven devices controlled by atomic-scale structural electronic effects at interfaces. Compared to conventional effect where channel conductivity is modulated carrier density modification, propagation distortions across an interface can control atomic scale bonding, interatomic electron tunneling rates thus mobility material. We use first-principles theory design atomically abrupt perovskite heterostructure involving...
Optical excitation of stripe-ordered La_{2-x}Ba_{x}CuO_{4} has been shown to transiently enhance superconducting tunneling between the CuO_{2} planes. This effect was revealed by a blueshift, or appearance Josephson plasma resonance in terahertz-frequency optical properties. Here, we show that this photoinduced state can be strengthened application high external magnetic fields oriented along c axis. For 7 T field, observe up tenfold enhancement transient interlayer phase correlation length,...
Recently, Freedman et al. [Phys. Rev. B 80, 064108 (2009)] calculated the elastic dipole tensor for several types of point defects in SrTiO3 and showed that it is nearly traceless oxygen vacancies. Thus, mobile vacancies are predicted to screen strain fields. Here, we report detailed diffuse x-ray scattering measurements bulk crystals prepared with controlled vacancy distributions. We verify nature an demonstrate both correlations between screening by
Through a combination of experimental measurements and theoretical modeling, we describe strongly orbital-polarized insulating ground state in an (LaTiO_{3})_{2}/(LaCoO_{3})_{2} oxide heterostructure. X-ray absorption spectra ab initio calculations show that electron is transferred from the titanate to cobaltate layers. The charge transfer, accompanied by large octahedral distortion, induces substantial orbital polarization layer size unattainable via epitaxial strain alone. asymmetry...
Epitaxial strain, layer confinement, and inversion symmetry breaking have emerged as powerful new approaches to control the electronic atomic-scale structural properties of complex metal oxides. Trivalent rare-earth (RE) nickelate $RE{\mathrm{NiO}}_{3}$ heterostructures been shown be exemplars since orbital occupancy, degeneracy, and, consequently, electronic/magnetic can altered a function epitaxial thickness, superlattice structure. One recent example is tricomponent...