Le Wang

Pacific Northwest National Laboratory

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Yingge Du

Pacific Northwest National Laboratory

Pingyun Feng

University of California, Riverside

Mark Bowden

Pacific Northwest National Laboratory

Scott A. Chambers

Pacific Northwest National Laboratory

Xianhui Bu

California State University, Long Beach

Tao Wu

Soochow University

Junling Wang

Guangdong University of Technology

Kuijuan Jin

Chinese Academy of Sciences

Shou‐Tian Zheng

Fuzhou University

Steven R. Spurgeon

National Renewable Energy Laboratory

Cooperative Institutions

Chinese Academy of Sciences

673

University of Chinese Academy of Sciences

311

University of Science and Technology of China

153

Institute of Physics

143

Zhejiang University

125

Shanghai Jiao Tong University

Peking University

Jilin University

Sichuan University

Huazhong University of Science and Technology

107

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Oxygen Vacancy Induced Room-Temperature Metal–Insulator Transition in Nickelate Films and Its Potential Application in Photovoltaics

ACS Applied Materials & Interfaces (2016)

Le Wang Sibashisa Dash Lei Chang Lü You Yaqing Feng

Oxygen vacancy is intrinsically coupled with magnetic, electronic, and transport properties of transition-metal oxide materials and directly determines their multifunctionality. Here, we demonstrate reversible control of oxygen content by postannealing at temperature lower than 300 °C and realize the reversible metal-insulator transition in epitaxial NdNiO₃ films. Importantly, over 6 orders of magnitude in the resistance modulation and a large change in optical bandgap are demonstrated at room temperature without destroying the parent framework and changing the p-type conductive mechanism. Further study revealed that oxygen vacancies stabilized the insulating phase at room temperature is universal for perovskite nickelate films. Acting as electron donors, oxygen vacancies not only stabilize the insulating phase at room temperature, but also induce a large magnetization of ∼50 emu/cm³ due to the formation of strongly correlated Ni²⁺ t(2g)⁶e(g)² states. The bandgap opening is an order of magnitude larger than that of the thermally driven metal-insulator transition and continuously tunable. Potential application of the newly found insulating phase in photovoltaics has been demonstrated in the nickelate-based heterojunctions. Our discovery opens up new possibilities for strongly correlated perovskite nickelates.

Metal–insulator transition

10.1021/acsami.6b00650

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Citations (112)

Current induced abnormal electroresistance effect observed in epitaxial La0.9Hf0.1MnO3 thin films

Journal of Applied Physics (2014)

Jie Xing Ju Gao Le Wang

La0.9Hf0.1MnO3 thin films with thickness 100 nm were prepared by using a pulsed laser deposition technique. Transport behaviors were investigated under various applied currents without an applied magnetic field. When the applied current is not too large, the peak value of the resistance gradually decreases with increasing current, demonstrating a normal electroresistance (ER) effect. However, when the current reaches a critical value, a high-resistance state appears at a lower temperature below the Curie temperature. And the appeared resistance peak at low temperature turns out to be extremely sensitive to a weak current. Even a very small current could greatly depress the height of the peak, an abnormal ER effect appears. Maximum resistance ratio ER, defined as [R(1 μA)-R(100 μA)]/R(100 μA), is about 1257% at 50 K. Physics related to the appearance of the novel state and the abnormal ER effect is discussed.

Pulsed Laser Deposition

10.1063/1.4879318

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Observation of unconventional chiral fermions with long Fermi arcs in CoSi

Nature (2019)

Zhicheng Rao Hang Li Tiantian Zhang Shangjie Tian Chenghe Li

Brillouin zone

Chirality

10.1038/s41586-019-1031-8

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Citations (316)

Influence of strain on SrFeO3-δ oxidation, reduction, and water dissociation: Insights from ambient pressure X-ray photoelectron spectroscopy

Applied Surface Science (2020)

Kelsey A. Stoerzinger Le Wang Hongyang Su Kyung Jae Lee Ethan J. Crumlin

Partial pressure

10.1016/j.apsusc.2020.146919

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Ultra-flat and long-lived plasmons in a strongly correlated oxide

Nature Communications (2022)

Han Gao Chao Ding Jaeseok Son Yangyu Zhu Mingzheng Wang

Plasmons in strongly correlated systems are attracting considerable attention due to their unconventional behavior caused by electronic correlation effects. Recently, flat plasmons with nearly dispersionless frequency-wave vector relations have drawn significant interest because of their intriguing physical origin and promising applications. However, these flat plasmons exist primarily in low-dimensional materials with limited wave vector magnitudes (q < ~0.7 Å-1). Here, we show that long-lived flat plasmons can propagate up to ~1.2 Å-1 in α-Ti2O3, a strongly correlated three-dimensional Mott-insulator, with an ultra-small energy fluctuation (<40 meV). The strong correlation effect renormalizes the electronic bands near Fermi level with a small bandwidth, which is responsible for the flat plasmons in α-Ti2O3. Moreover, these flat plasmons are not affected by Landau damping over a wide range of wave vectors (q < ~1.2 Å-1) due to symmetry constrains on the electron wavefunctions. Our work provides a strategy for exploring flat plasmons in strongly correlated systems, which in turn may give rise to novel plasmonic devices in which flat and long-lived plasmons are desirable.

10.1038/s41467-022-32359-0

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Multishelled Nickel–Cobalt Oxide Hollow Microspheres with Optimized Compositions and Shell Porosity for High-Performance Pseudocapacitors

ACS Applied Materials & Interfaces (2016)

Xiangcun Li Le Wang Jianhang Shi Naixu Du Gaohong He

Nickel–cobalt oxides/hydroxides have been considered as promising electrode materials for a high-performance supercapacitor. However, their energy density and cycle stability are still very poor at high current density. Moreover, there are few reports on the fabrication of mixed transition-metal oxides with multishelled hollow structures. Here, we demonstrate a new and flexible strategy for the preparation of hollow Ni–Co–O microspheres with optimized Ni/Co ratios, controlled shell porosity, shell numbers, and shell thickness. Owing to its high effective electrode area and electron transfer number (n3/2 A), mesoporous shells, and fast electron/ion transfer, the triple-shelled Ni–Co1.5–O electrode exhibits an ultrahigh capacitance (1884 F/g at 3A/g) and rate capability (77.7%, 3–30A/g). Moreover, the assembled sandwiched Ni–Co1.5–O//RGO@Fe3O4 asymmetric supercapacitor (ACS) retains 79.4% of its initial capacitance after 10 000 cycles and shows a high energy density of 41.5 W h kg–1 at 505 W kg–1. Importantly, the ACS device delivers a high energy density of 22.8 W h kg–1 even at 7600 W kg–1, which is superior to most of the reported asymmetric capacitors. This study has provided a facile and general approach to fabricate Ni/Co mixed transition-metal oxides for energy storage.

Pseudocapacitor

Cobalt oxide

Nickel oxide

10.1021/acsami.6b04654

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Citations (88)

Quantification of Oxygen Vacancies in SrFe_0.5Cr_0.5O_3−δ Thin Films: Correlating Lattice Expansion with Oxidation State Variability

ACS Applied Electronic Materials (2025)

Mohammad Delower Hossain Krishna Prasad Koirala Le Wang Widitha Samarakoon Mark Bowden

Oxygen vacancies (VO), even in the dilute regime, can significantly impact the physical and chemical properties of complex oxides. It is however challenging to reliably detect and adequately quantify such defects in thin film samples where the VO concentration and distribution may further vary in response to interfacial strain. Here, we present a method to quantify VO concentrations in SrFe0.5Cr0.5O3−δ (SFCO) epitaxial thin films. Through coherent Bragg rod analysis, X-ray absorption spectroscopy, and theoretical modeling, we systematically correlate the c-axis lattice expansion detected in SFCO films with a VO concentration gradient. Our results reveal a nearly linear relationship between oxygen off-stoichiometry and out-of-plane lattice expansion in coherently strained SFCO films, with δ increasing from 0.32 to 0.52 and the lattice expanding by ∼1.0%. Moreover, a significant decrease in Cr oxidation state (from Cr5+ to Cr3+) is observed as the VO concentration increases, while the Fe oxidation state remains fixed at Fe3+. Our findings provide a reliable way to quantify oxygen stoichiometry in complex oxides, offering a pathway to design materials with precisely tailored structure–property relationships.

Lattice (music)

Oxidation state

10.1021/acsaelm.4c02149

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Propagation property of Laguerre-Gaussian beams carrying fractional orbital angular momentum in an underwater channel

OSA Continuum (2019)

Wenhao Zhang Le Wang Wennai Wang Shengmei Zhao

In the paper, we experimentally demonstrate the propagation property of Laguerre-Gaussian (LG) beams carrying fractional orbital angular momentum (FOAM) in an underwater environment. The effects of topological charge (TC), temperature gradient, and salinity on the transmission of the LG-FOAM beam in underwater turbulence are analyzed, and the optimum interval of TC for FOAM communication and their help for the improvement of system capacity are discussed. The results show that both the salinity and the temperature gradient have serious impacts on the beam, and meanwhile, the temperature gradient plays a heavier influence. Although the detection probability of one FOAM mode at the receiver side is lower than that nearest integer OAM mode, in the case of that topological charges used are limited, the interval-based mode-multiplexed communication using FOAM can increase the channel capacity.

Laguerre polynomials

Gaussian beam

Mode (computer interface)

Momentum (technical analysis)

Temperature salinity diagrams

10.1364/osac.2.003281

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Citations (16)

Outdoor Personnel Positioning System Based on GPS

Applied Mechanics and Materials (2013)

Hongbo Pan Le Wang Dong Dong Chen

With the comparison of wireless positioning technology such as Wi-Fi, ZigBee, GPS, this paper presents an outdoor personnel positioning system based on GPS. It is composed of electronic wristbands (used for detainees), handsets (used for supervisors) and monitoring software of the host computer. In order to improve the positioning accuracy and reduce power consumption of the system, high-precision GPS chips and low power microcontroller chips are applied. Handsets can exchange data with electronic wristbands through self-prepared communication protocol. It also can work out the distance through a precise latitude and longitude distance algorithm. Finally, the monitoring software will reproduce personnel routes in Google Earth. The system can achieve the positioning of fixed groups and moving groups, which is suitable for the detention center to supervise, escort or chase detainees.

Hybrid positioning system

Geographic coordinate system

10.4028/www.scientific.net/amm.385-386.1537

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On seismic intensification in some brick-concrete structure teaching building

Shanxi Architecture (2010)

Le Wang

By combining with the projects,the paper illustrates the seismic intensification scheme for the brick-concrete structure,including the intensification in the brick-concrete and brick pilaster,the addition of the constructional column,the staircase rest and the intensification of platform,so as to ensure the wholeness of the teaching building and the seismic performance can be improved.

Brick

Rest (music)

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