Article
Materials Science, Ceramics
Yunpeng Qu, Chuanbing Cheng, Rongwei Ma, Runhua Fan
Summary: In this study, graphene-carbon nanotube/copper calcium titanate ceramic nanocomposites were prepared using spark plasma sintering technology, showing a correlation between the content of graphene-carbon nanotubes and epsilon-negative property. By constructing three-dimensional graphene-carbon nanotube networks in the ceramics, epsilon-negative and epsilon-near-zero properties were achieved. Additionally, dielectric loss behavior and impedance response were discussed, and the inductive character of epsilon-negative materials was explained through equivalent circuit analysis.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Physical
Ryan Bower, Matthew P. Wells, Freya Johnson, Rebecca Kilmurray, Brock Doiron, Eleonora Cali, Giuseppe Mallia, Bin Zou, Andrei P. Mihai, Nicholas M. Harrison, Sarah Fearn, Rupert Oulton, Neil McN. Alford, Lesley F. Cohen, Peter K. Petrov
Summary: This study investigates the optical response and electrical properties of reactively sputtered niobium oxynitride thin films through experimental and computational simulations. The experimental results show that these films have screened plasma wavelengths tunable over a range of 90 nm, and exhibit a double epsilon-near-zero behavior. This behavior is attributed to the incorporation of oxygen into the films during deposition.
APPLIED SURFACE SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Dipa Ghindani, Alireza R. Rashed, Mohsin Habib, Humeyra Caglayan
Summary: This work demonstrates the active tuning of coupling strength in a strongly coupled system comprised of a thin epsilon-near-zero material and gold nanorods. A novel gating scheme using an ionic liquid is developed to bias the system and tune the coupling in transmission mode, resulting in a significant tuning of the coupled resonance up to 30 nm by changing bias voltages from 0 to 4.5 V. This control mechanism on strong coupling offers exciting opportunities for various disruptive applications by providing advanced control and tunability.
ADVANCED OPTICAL MATERIALS
(2021)
Article
Optics
Feng Wu, Dejun Liu, Xiaohu Wu, Hongju Li, Shuyuan Xiao
Summary: In this paper, a frequency-tunable wide-angle polarization selection based on an anisotropic epsilon-near-zero metamaterial is achieved using a subwavelength graphene/SiO2 multilayer. By changing the gate voltage applied to the graphene, the operating frequency of polarization selection can be flexibly tuned. This polarization selector has potential applications in various fields.
Article
Optics
Yaping Hou, Lin Cheng, Zhengji Wen, Tianlun Li, Jianyong Mao, Yunfan Xu, Fu Liu, Jiaming Hao, Weitao Jiang, Yanpeng Zhang, Lei Zhang
Summary: A sandwich-type nonlinear nanoantenna with a thin layer of epsilon-near-zero (ENZ) material is proposed, which can dynamically tune the far-field scattering via an all-optical approach. By combining the dependence of four fundamental Mie modes on refractive index and intensity-dependent refractive index change caused by nonlinear optical effect in ENZ material, the far-field scattering can be controlled by controlling the intensity of incident light. The proposed all-optical nonlinear nanoantennas have promising applications in all-optical light modulation for photonic devices.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Ji Dai, Haitao Jiang, Zhiwei Guo, Jun Qiu
Summary: A self-organized polyolefin elastomer@Graphene/Carbon nanotube metacomposite with unique adjustable epsilon-and-mu-near-zero (EMNZ) properties is innovatively achieved in this paper. The EMNZ performance can be conveniently and precisely altered by adjusting the component content within the broadband frequency range.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Optics
Yu-bo Li, Hao-yuan Song, Yu-qi Zhang, Sheng Zhou, Shu-fang Fu, Qiang Zhang, Xuan-Zhang Wang
Summary: We examined the Goos-Haenchen (GH) and Imbert-Fedorov (IF) shifts of the reflective beam from hexagonal boron nitride (hBN) covered by black phosphorus (BP) layers rotated at an angle to the incident plane. The GH and IF shifts are determined by the interaction of phonon polaritons in hBN and plasmon polaritons in BP, as well as the structure surface and interface between the two media. The GH shift can be continuously tuned by adjusting the electron density and anisotropic axis-orientation of BP, and the IF shift can be greatly improved even up to -156 times the wavelength λ0.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Optics
Lin Cheng, Kun Huang, Yu Wang, Fan Wu
Summary: Epsilon-near-zero nanoantennas based on indium tin oxide (ITO) are proposed to tune the far-field radiation pattern. The deflection angle changes 17 degrees as incident intensities increase. By employing an array of ITO or hybrid nanodisks, the unidirectionality of the radiation pattern is enhanced, resulting in a needle-like shape with an angular beam width a < 8 degrees of the main lobe. The deflection angle of the radiation pattern response with the needle-like lobe paves the way for further studies and applications in beam steering and optical modulation.
Article
Optics
Arash Nemati, Qian Wang, Norman Soo Seng Ang, Weide Wang, Minghui Hong, Jinghua Teng
Summary: The study utilizes the lossy nature of indium tin oxide (ITO) at epsilon-near-zero (ENZ) wavelength to design an electrically tunable metasurface absorber, achieving total absorption of reflected light through coupling of magnetic dipole resonance with ENZ wavelength. The metasurface can achieve high modulation depth at a specific bias voltage and is insensitive to incident light polarization due to its circular resonator design and symmetrical bias connections.
OPTO-ELECTRONIC ADVANCES
(2021)
Article
Optics
Lin Zhao, Ning Wang, Hongwei Fu, Siyao Yu
Summary: This paper introduces a novel tunable optical transmission structure by nesting multiple dielectric dopants in epsilon-near-zero media, providing a new way for developing optical (electromagnetic) wavefront tunable devices. The structure is capable of real-time manipulation of transmission wave properties by replacing or moving internal dielectric cylinders, as demonstrated at microwave frequencies using a rectangular waveguide.
Article
Physics, Condensed Matter
Tanmay Bhowmik, Jegyasu Gupta, Debabrata Sikdar
Summary: Control of polarization states of light is crucial for any photonic system. However, conventional polarization-controlling elements are typically static and bulky. Metasurfaces open a new paradigm to realize flat optical components by engineering meta-atoms at sub-wavelength scale. Tunable metasurfaces can provide enormous degrees-of-freedom to tailor electromagnetic properties of light and thus have the potential to realize dynamic polarization control in nanoscale.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Optics
Tanmay Bhowmik, Debabrata Sikdar
Summary: In this Letter, a grating-assisted dual-band metasurface for spatial light modulation is proposed, which can operate at specific wavelengths in the C-band and O-band. By leveraging the properties of the silicon-nitride nanograting and the silicon-indium-tin-oxide (ITO)-alumina-gold stack, the reflectance spectra can be modulated at 1.55 mu m and 1.31 mu m wavelengths. This metasurface may offer potential applications in the development of dual-band active nanophotonic devices.
Article
Chemistry, Physical
Hang Jiang, Yuanan Zhao, Hao Ma, Cao Feng, Yi Wu, Weili Zhang, Meiling Chen, Mengxia Wang, Yafei Lian, Zhaoliang Cao, Jianda Shao
Summary: A new design concept for broadband light absorption based on the coupling of epsilon-near-zero (ENZ) and localized surface plasmon resonance (LSPR) modes is proposed. Experimental results show that a single-layer patterned indium tin oxide (ITO) film on a two-dimensional microsphere array can achieve over 98% light absorption in a wide wavelength range. These findings provide a low-cost solution for designing broadband perfect absorbers based on ENZ materials, with potential applications in near-infrared sensors, photoelectric detection, and ENZ photonics.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Applied
Yaping Hou, Jianyong Mao, Tianlun Li, Yunfan Xu, Weitao Jiang, Yanpeng Zhang, Lei Zhang
Summary: An all-optical approach is proposed to actively control the polarization state of near-infrared light at the nanoscale using a nonlinear metasurface. By exploiting the intense refractive index change of epsilon-near-zero (ENZ) materials, the phase difference between two orthogonal electric fields at ENZ wavelength can be continuously tuned by varying the incident light power. This allows the polarization state of the reflected light to be actively tuned from linear to circular state. The proposed all-optical approach holds promise for tunable photonic functionalities in practical applications.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Materials Science, Ceramics
Yunpeng Qu, Peitao Xie, Yunlei Zhou, Junfei Ding, Yanli Chen, Xiu Gong, Jingliang Yang, Qiong Peng, Xiaosi Qi
Summary: This study presents a composite material consisting of CaCu3Ti4O12 and graphitized-multiwall carbon nanotube designed based on electronic structure and percolation theory. The composite material exhibits a switchable response from positive to negative permittivity with increasing frequency and achieves tunable epsilon'-near-zero effect. The composite material shows excellent electromagnetic shielding performance at specific frequencies.
CERAMICS INTERNATIONAL
(2023)
Article
Chemistry, Multidisciplinary
Wanying Li, Yimeng Guo, Zhaoping Luo, Shuhao Wu, Bo Han, Weijin Hu, Lu You, Kenji Watanabe, Takashi Taniguchi, Thomas Alava, Jiezhi Chen, Peng Gao, Xiuyan Li, Zhongming Wei, Lin-Wang Wang, Yue-Yang Liu, Chengxin Zhao, Xuepeng Zhan, Zheng Vitto Han, Hanwen Wang
Summary: This study successfully demonstrated a gate-programmable non-volatile memory by vertically assembling graphite, CuInP2S6, and MoS2 layers into a metal-ferroelectric-semiconductor (M-FE-S) architecture. The resulting devices integrate the functionalities of both ferroelectric memristor (FE-memristor) and metal-oxide-semiconductor field-effect transistor (MOS-FET), enabling gate-tunable giant electroresistance with multi-level ON-states in the FE-memristor. First-principles calculations revealed that this behavior originates from the specific band alignment at the FE-S interface. These findings pave the way for engineering ferroelectricity-mediated memories in future implementations of 2D nanoelectronics.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Nikhil Tilak, Guohong Li, Takashi Taniguchi, Kenji Watanabe, Eva Y. Andrei
Summary: Artificially twisted heterostructures of semiconducting transition-metal dichalcogenides (TMDs) provide control over their electronic and optical properties via spatial modulation of interlayer interactions and structural reconstruction. This study investigates twisted MoS2 bilayers at twist angles near 0 degrees using scanning tunneling microscopy/spectroscopy. The moire pattern, dominated by lattice reconstruction for small angles, reveals large triangular domains with rhombohedral stacking. Spectroscopy measurements show a strong moire potential for angles below 3 degrees. In reconstructed regions, an asymmetry between neighboring domains is observed, which is attributed to the vertical polarization intrinsic to rhombohedral stacked TMDs. This study offers insights into interfacial ferroelectrics and has implications for designing novel heterostructures harnessing this effect.
Article
Chemistry, Multidisciplinary
Michael Neumann, Xu Wei, Luis Morales-Inostroza, Seunghyun Song, Sung-Gyu Lee, Kenji Watanabe, Takashi Taniguchi, Stephan Goetzinger, Young Hee Lee
Summary: The discovery of room-temperature single-photon emitters in two-dimensional hexagonal boron nitride has generated significant research interest. The origin of these emitters has been found to be organic molecules, possibly aromatic fluorophores. This finding has important implications for the understanding and utilization of single-photon emitters.
Article
Physics, Multidisciplinary
Yalong Yuan, Yanbang Chu, Cheng Hu, Jinpeng Tian, Le Liu, Fanfan Wu, Yiru Ji, Jiaojiao Zhao, Zhiheng Huang, Xiaozhou Zan, Luojun Du, Kenji Watanabe, Takashi Taniguchi, Dongxia Shi, Zhiwen Shi, Wei Yang, Guangyu Zhang
Summary: We demonstrate the epitaxial growth of trilayer graphene moire superlattice on hexagonal boron nitride using remote plasma-enhanced chemical vapor deposition. The resulting TLG/hBN exhibits a uniform moire pattern with a period of about 15 nm, showing strong electron-electron correlation and quantum Hall states. Our work suggests that epitaxy provides an easy and reproducible method for fabricating stable two-dimensional strongly correlated electronic materials.
Article
Chemistry, Multidisciplinary
Paritosh Karnatak, Zarina Mingazheva, Kenji Watanabe, Takashi Taniguchi, Helmuth Berger, Laszlo Forro, Christian Schoenenberger
Summary: The study reveals that subgap excitations emerge on NbSe2 when MoS2 or hexagonal boron nitride (hBN) is used as the tunnel barrier. By investigating various heterostructure designs, the origin of these excitations is probed. Defect states at the edge of NbSe2 strongly couple to the superconductor, forming Andreev bound states. Moreover, the absence of subgap states in hBN tunnel barriers compared to the widespread presence in MoS2 tunnel barriers suggests defects in MoS2 as their origin. The magnetic nature of these excitations indicates a singlet- or a doublet-type ground state, emphasizing the role of strong spin-orbit coupling based on nearly vanishing g factors or avoided crossings.
Article
Multidisciplinary Sciences
Mir Mohammad Sadeghi, Yajie Huang, Chao Lian, Feliciano Giustino, Emanuel Tutuc, Allan H. MacDonald, Takashi Taniguchi, Kenji Watanabe, Li Shi
Summary: The peculiar electron-phonon interaction in graphene heterostructures enables ultrahigh mobility, electron hydrodynamics, superconductivity, and superfluidity. A peak in the Lorenz ratio near 60 kelvin and its decrease with increased mobility are observed in degenerate graphene, indicating an unusual behavior. This experimental observation, combined with ab initio calculations and analytical models, suggests that broken reflection symmetry in graphene heterostructures can relax the selection rule for electron coupling with flexural phonons, contributing to the increase of the Lorenz ratio at intermediate temperatures.
Article
Optics
Fedele Tagarelli, Edoardo Lopriore, Daniel Erkensten, Rauel Perea-Causin, Samuel Brem, Joakim Hagel, Zhe Sun, Gabriele Pasquale, Kenji Watanabe, Takashi Taniguchi, Ermin Malic, Andras Kis
Summary: This study reveals the dipole-dependent properties and transport of excitons with different degrees of hybridization by modulating the layer hybridization and interplay between many-body interactions of excitons in a van der Waals heterostructure with an applied vertical electric field. Moreover, it is found that emission quantum yields of the transporting species remain constant as a function of excitation power, with radiative decay mechanisms dominating over nonradiative ones, which is a fundamental requirement for efficient excitonic devices. These findings have crucial implications for studying emerging states of matter and optoelectronic applications based on exciton propagation.
Article
Materials Science, Multidisciplinary
Jonathan Bradford, Tin S. Cheng, Tyler S. S. James, Andrei N. Khlobystov, Christopher J. Mellor, Kenji Watanabe, Takashi Taniguchi, Sergei Novikov, Peter H. Beton
Summary: The integration of graphene and hexagonal boron nitride (hBN) in lateral heterostructures allows for engineering the material properties through quantum confinement or introduction of novel electronic and magnetic states at the interface.In this study, graphene nanoribbons(GNRs) passivated by hBN were grown via high-temperature molecular beam epitaxy (HT-MBE) on pre-etched hBN trenches.High-resolution atomic force microscopy(AFM) showed that GNRs grew epitaxially and formed a network passivated by hBN.It was observed using conductive AFM that quasiparticle interference patterns caused by intervalley scattering at the graphene/hBN interface had implications for the potential transport characteristics of hBN passivated GNR devices.
Article
Chemistry, Multidisciplinary
Souvik Biswas, Joeson Wong, Supavit Pokawanvit, Wei-Chang David Yang, Huairuo Zhang, Hamidreza Akbari, Kenji Watanabe, Takashi Taniguchi, Albert V. Davydov, Felipe H. da Jornada, Harry A. Atwater
Summary: By characterizing and calculating the structure of the edges of black phosphorus (BP), researchers have discovered that certain atomic reconstructions on the edges can strongly confine excitons, resulting in unique emission features. They have also demonstrated efficient electrically-controlled emission from localized edge excitons. These findings provide insights for exploring nanoribbons and quantum dots as hosts for narrowband light generation.
Article
Chemistry, Multidisciplinary
Xiangyan Han, Qianling Liu, Yijie Wang, Ruirui Niu, Zhuangzhuang Qu, Zhiyu Wang, Zhuoxian Li, Chunrui Han, Kenji Watanabe, Takashi Taniguchi, Zhida Song, Jinhai Mao, Zheng Vitto Han, Zizhao Gan, Jianming Lu
Summary: Rhombohedral trilayer graphene is a natural flat-band platform for studying interaction-driven symmetry-breaking phases. The displacement field can further flatten the band and enhance the density of states, controlling the energy balance between spin and valley degrees of freedom. In this work, the authors characterized the isospin flavor polarization and developed a method to measure the chemical potential at a fixed displacement field, allowing for the extraction of energy variation during phase transitions. This work opens opportunities for the thermodynamic characterization of displacement-field tuned van der Waals heterostructures.
Article
Nanoscience & Nanotechnology
Gabriele Pasquale, Edoardo Lopriore, Zhe Sun, Kristians Cernevics, Fedele Tagarelli, Kenji Watanabe, Takashi Taniguchi, Oleg V. Yazyev, Andras Kis
Summary: In this study, indium selenide (InSe) is used as a two-dimensional flat-band system to investigate tunnelling photocurrents. The presence of van Hove singularity at the flat band is found to cause a sharp change in tunnelling mechanisms. Tunnelling currents are shown to be a reliable probe for detecting the energy position of the van Hove singularity in a van der Waals flat-band system, even at room temperature.
NATURE NANOTECHNOLOGY
(2023)
Article
Multidisciplinary Sciences
Qianying Hu, Zhen Zhan, Huiying Cui, Yalei Zhang, Feng Jin, Xuan Zhao, Mingjie Zhang, Zhichuan Wang, Qingming Zhang, Kenji Watanabe, Takashi Taniguchi, Xuewei Cao, Wu-Ming Liu, Fengcheng Wu, Shengjun Yuan, Yang Xu
Summary: Researchers demonstrate the spatial confinement and manipulation of Rydberg moire excitons through two-dimensional moire superlattices, indicating their potential for quantum technologies.
Article
Multidisciplinary Sciences
Suman Chatterjee, Medha Dandu, Pushkar Dasika, Rabindra Biswas, Sarthak Das, Kenji Watanabe, Takashi Taniguchi, Varun Raghunathan, Kausik Majumdar
Summary: Excitonic states trapped in harmonic moire wells of twisted heterobilayers offer a unique platform for studying many-body physics. In this study, we demonstrate anharmonic tuning of the moire potential in a WS2/WSe2 heterobilayer through gate voltage and optical power. By applying a gate voltage, we can observe both linear and parabolic Stark shifts for the ground state and first excited state, respectively, of the moire-trapped exciton. Additionally, the exciton localization-dependent dipolar repulsion results in a power-induced blueshift that is five times greater than previous reports.
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Tim Voelzer, Alina Schubert, Erik von der Oelsnitz, Julian Schroeer, Ingo Barke, Rico Schwartz, Kenji Watanabe, Takashi Taniguchi, Sylvia Speller, Tobias Korn, Stefan Lochbrunner
Summary: This study investigates the charge or energy transfer-related quenching of perylene orange (PO) dye fluorescence when brought onto monolayer TMDCs via thermal vapor deposition. The results show a significant intensity drop in PO fluorescence and a relative growth of trion versus exciton contribution in TMDC emission. Fluorescence imaging lifetime microscopy confirms the intensity quenching to be around 10^3-fold and a drastic reduction in lifetime. Analysis suggests a time constant of several picoseconds at most, indicating efficient charge separation suitable for optoelectronic devices.
NANOSCALE ADVANCES
(2023)
Article
Physics, Applied
Nadezda Varkentina, Yves Auad, Steffi Y. Woo, Florian Castioni, Jean-Denis Blazit, Marcel Tence, Huan-Cheng Chang, Jeson Chen, Kenji Watanabe, Takashi Taniguchi, Mathieu Kociak, Luiz H. G. Tizei
Summary: Electron-photon temporal correlations in electron energy loss spectroscopy and cathodoluminescence spectroscopy have been used to measure the relative quantum efficiency of materials. It has been found that cathodoluminescence excitation spectroscopy can also be used to measure the decay time of excitations and explore the energy dependence of decay time. By using well-known insulating materials, nanodiamonds with NV0 defects and hexagonal boron nitride with 4.1 eV defects, the instrumental response function has been characterized, and the measured lifetimes of the defects match previous reports.
APPLIED PHYSICS LETTERS
(2023)
