A5055318354- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- Multiferroics and related materials
- Ferroelectric and Piezoelectric Materials
- Physics of Superconductivity and Magnetism
- Planetary Science and Exploration
- Astro and Planetary Science
- Topological Materials and Phenomena
- Semiconductor materials and devices
- Inorganic Chemistry and Materials
- Microwave Dielectric Ceramics Synthesis
- Advanced ceramic materials synthesis
- Theoretical and Computational Physics
- ZnO doping and properties
- Perovskite Materials and Applications
- Magnetic properties of thin films
- Transition Metal Oxide Nanomaterials
- Catalytic Processes in Materials Science
- Scientific Research and Discoveries
- Ion-surface interactions and analysis
- Space Exploration and Technology
- Nuclear materials and radiation effects
- Electrical and Thermal Properties of Materials
- Advancements in Solid Oxide Fuel Cells
Rutgers, The State University of New Jersey
2016-2025
Rütgers (Germany)
2020
Rutgers Sexual and Reproductive Health and Rights
2020
Indian Institute of Science Bangalore
2019
University of Arkansas at Fayetteville
2008-2017
Argonne National Laboratory
2015
Lawrence Berkeley National Laboratory
2015
Using resonant X-ray spectroscopies combined with density functional calculations, we find an asymmetric bi-axial strain-induced $d$-orbital response in ultra-thin films of the correlated metal LaNiO$_3$ which are not accessible bulk. The sign misfit strain governs stability octahedral "breathing" distortion, which, turn, produces emergent charge-ordered ground state altered ligand-hole and bond covalency. Control this new mechanism opens a pathway to rational orbital engineering, providing...
We investigate the electronic reconstruction in (LaNiO$_{3}$)$_n$/(LaAlO$_{3}$)$_3$ (n=3, 5 and 10) superlattices due to quantum confinement (QC) by d.c. transport resonant soft x-ray absorption spectroscopy. In proximity QC limit, a Mott-type transition from an itinerant electron behavior localized state is observed. The system exhibits tendency towards charge-order during transition. ab initio cluster calculations are good agreement with spectra, indicating that apical ligand hole density...
In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO$_3$ have inspired a wealth exciting experimental theoretical results. However, to date there is very limited understanding the states emerging after interfacial charge-transfer their connections modified band structure at interface. Towards this goal, we synthesized prototypical superlattice composed correlated metal doped Mott insulator LaTiO$_{3+\delta}$, investigated its by...
We have synthesized epitaxial NdNiO$_{3}$ ultra-thin films in a layer-by-layer growth mode under tensile and compressive strain on SrTiO$_{3}$ (001) LaAlO$_3$ (001), respectively. A combination of X-ray diffraction, temperature dependent resistivity, soft absorption spectroscopy has been applied to elucidate electronic structural properties the samples. In contrast bulk NdNiO$_{3}$, metal-insulator transition is found be completely quenched, while remains albeit modified from behavior.
In pursuit of rational control orbital polarization, we present a combined experimental and theoretical study single-unit-cell superlattices the correlated metal LaNiO3 band insulator LaAlO3. Polarized X-ray absorption spectra show distinct asymmetry in response under strain. A splitting energies consistent with octahedral distortions is found for case compressive sharp contrast, tensile strain, no although strong polarization present. Density functional theory calculations including Hubbard...
An optical study of NdNiO(3) ultrathin films with insulating and metallic ground states reveals new aspects the insulator-to-metal transition that point to Mott physics as driving force. In contrast behavior charge-ordered systems, we find emergence Drude resonance across is linked a spectral weight transfer over an energy range order Coulomb repulsion U, gap filled instead closing continuously.
Polar metals, commonly defined by the coexistence of polar crystal structure and metallicity, are thought to be scarce because long-range electrostatic fields favoring expected fully screened conduction electrons a metal. Moreover, reducing from three two dimensions, it remains an open question whether metal can exist. Here we report on realization room temperature two-dimensional B-site type in tri-color (tri-layer) superlattices BaTiO$_3$/SrTiO$_3$/LaTiO$_3$. A combination atomic...
Pyrochlore materials are known for their exotic magnetic and topological phases arising from complex interactions among electron correlations, band topology, geometric frustration. Interfaces between different pyrochlore crystals characterized by many-body ground states hold immense potential novel interfacial phenomena due to the strong these phases. However, realization of such interfaces has been severely hindered limitations in material synthesis methods. In this study, we discover a...
By using an alternative wet-etch procedure, we have obtained high-quality atomically flat TiO2 terminated surfaces of SrTiO3 single crystals with the morphology equivalent to that conventional methods. applying a combined power photoluminescence (PL) spectroscopy, reflection high-energy electron diffraction, atomic force microscopy imaging, and soft x-ray absorption (XAS), were able identify monitor complex evolution oxygen defect states Ti valency at surface near-surface layers. Our...
We address the fundamental issue of growth perovskite ultra-thin films under condition a strong polar mismatch at heterointerface exemplified by correlated metal LaNiO3 on band insulator SrTiO3 along pseudo cubic [111] direction. While in general metallic film can effectively screen this polarity mismatch, we establish that limit, are insulating nature and require additional chemical structural reconstruction to compensate for such mismatch. A combination in-situ reflection high-energy...
An optical study of fully strained ultrathin ${\mathrm{LaNiO}}_{3}$ films is presented and compared with LDA + DMFT calculations. were grown by pulsed laser deposition on ${\mathrm{LaAlO}}_{3}$ ${\mathrm{SrTiO}}_{3}$ substrates which provide compressive tensile strain, respectively. Optical conductivity data show a Drude peak spectral weight that significantly reduced to obtained from The extended analysis reveals the presence pseudogap around 80 meV for film near 40 meV, at low temperature...
Deterministic control over the periodic geometrical arrangement of constituent atoms is backbone material properties, which, along with interactions, define electronic and magnetic ground state. Following this notion, a bilayer prototypical rare-earth nickelate, NdNiO_{3}, combined dielectric spacer, LaAlO_{3}, has been layered pseudocubic [111] direction. The resulting artificial graphenelike Mott crystal 3d electrons antiferromagnetic correlations. In addition, combination resonant X-ray...
The epitaxial stabilization of a single layer or superlattice structures composed complex oxide materials on polar (111) surfaces is severely burdened by the reconstructions at interface that commonly arise to neutralize polarity. We report synthesis high quality LaNiO3/mLaAlO3 pseudo cubic superlattices (111)-oriented LaAlO3, proposed candidate for topological insulating behavior. Comprehensive X-Ray diffraction measurements, reflection energy electron diffraction, and element specific...
In all archetypical reported (001)-oriented perovskite heterostructures, it has been deduced that the preferential occupation of two-dimensional electron gases is in-plane $d_\textrm{xy}$ state. sharp contrast to this, investigated electronic structure a spinel-perovskite heterostructure $\gamma$-Al$_2$O$_3$/SrTiO$_3$ by resonant soft X-ray linear dichroism, demonstrates out-of-plane $d_\textrm{xz}$/$d_\textrm{yz}$ states for interfacial electrons. Moreover, impact strain further...
We investigate [Formula: see text]/[Formula: text] superlattices in which we observe a full electron transfer at the interface from Ir to Ni, triggering massive structural and electronic reconstruction. Through experimental characterization first-principles calculations, determine that large crystal field splitting distorted interfacial octahedra surprisingly dominates over spin-orbit coupling together with Hund's results high-spin (S = 1) configurations on both Ni sites. This demonstrates...
The metal-insulator transition and the underlying electronic orbital structure in e(g)(1) quantum wells based on NdNiO3 were investigated by dc transport resonant soft x-ray absorption spectroscopy. By comparing of same dimension but with two different confinement structures, we explicitly demonstrate that well boundary condition correlated electrons is critical to selecting many-body ground state. In particular, long-range orderings are found be strongly enhanced under sandwiching NdNiO(3)...
A series of ultrathin epitaxial films EuNiO${}_{3}$ (ENO) were grown on a set substrates traversing from compressive ($\ensuremath{-}2.4%$) to tensile (+2.5%) lattice mismatch. On moving strain, transport measurements demonstrate successively suppressed Mott insulating behavior eventually resulting in complete suppression the state at high strain. Corroborating these findings, resonant soft x-ray absorption spectroscopy Ni ${L}_{3,2}$ edge reveals presence strong multiplet splitting strained...
We report on the selective fabrication of high-quality Sr$_2$IrO$_4$ and SrIrO$_3$ epitaxial thin films from a single polycrystalline target by pulsed laser deposition. Using combination X-ray diffraction photoemission spectroscopy characterizations, we discover that within relatively narrow range substrate temperature, oxygen partial pressure plays critical role in cation stoichiometric ratio films, triggers stabilization different Ruddlesden-Popper (RP) phases. Resonant absorption...
Ultrathin SrRuO${}_{3}$ has a nontrivial Hall response that looks strikingly like skyrmion-induced topological effect. Here, the authors demonstrate how Berry phase alone, without skyrmions, provides comprehensive explanation for such response. The contribution to effect can be altered, enhanced, and even change sign in number of layers, temperature, and, importantly, disorder. By comparing effects disorder, theoretically, on skyrmion model spin-orbit coupled model, only latter capture...
The interplay between electronic interactions and strong spin-orbit coupling is expected to create a plethora of fascinating correlated topological states quantum matter. Of particular interest are magnetic Weyl semimetals originally proposed in the pyrochlore iridates, which only reveal their nature thin film form. To date, however, direct experimental demonstrations these exotic phases remain elusive, due lack usable single crystals insufficient quality available films. Here, we report on...
Depth-resolved cathodoluminescence spectroscopy of atomically flat TiO2-terminated SrTiO3 single crystal surfaces reveals dramatic differences in native point defects produced by conventional etching with buffered HF (BHF) and an alternative procedure using HCl–HNO3 acidic solution (HCLNO), which produces three times fewer oxygen vacancies before nearly order magnitude after pure annealing. BHF-produced defect densities extend hundreds nanometers below the surface, whereas lower...
We have conducted a detailed microscopic investigation of [LaNiO3(1 u.c.)/LaAlO3(1 u.c.)]N superlattices grown on (001) SrTiO3 and LaAlO3 to explore the influence polar mismatch resulting electronic structural properties. Our data demonstrate that initial growth nonpolar surface leads rough morphology unusual 2+ valence Ni in LaNiO3 layer, which is not observed after LaAlO3. A devised model suggests can be resolved if perovskite layers grow with an excess LaO, also accounts for electronic,...
We report on a systematic study of the temperature-dependent Hall coefficient and thermoelectric power in ultrathin metallic LaNiO${}_{3}$ films that reveal strain-induced, self-doping carrier transition is inaccessible bulk. As film strain varies from compressive to tensile at fixed composition stoichiometry, evolution transport coefficients strikingly similar those bulk hole-doped superconducting cuprates with varying doping level. Density functional calculations strain-induced changes...