Article
Chemistry, Multidisciplinary
Anna Kuzmina, Markus Parzefall, Patrick Back, Takashi Taniguchi, Kenji Watanabe, Achint Jain, Lukas Novotny
Summary: By controlled stacking of graphene layers, the limitation of single-layer graphene as a material for light-emitting devices has been overcome, enabling twist-controlled resonant light emission. Experimental findings show light emission irrespective of the crystallographic alignment between the graphene electrodes, with a spectrally tunable resonant peak in the near-infrared range.
Article
Chemistry, Multidisciplinary
Alexander Mehler, Nicolas Neel, Elena Voloshina, Yuriy Dedkov, Jorg Kroger
Summary: The study demonstrates the growth of graphene on h-BN through thermal decomposition and catalytic assistance of metal substrates, as well as the epitaxial growth of h-BN on Pt(111). Different honeycomb structures of graphene on h-BN and the observation of distinct superstructures at small probe-surface distances are highlighted in this study.
Article
Chemistry, Multidisciplinary
Binghe Xie, Zijie Ji, Jiaxin Wu, Ruan Zhang, Yunmin Jin, Kenji Watanabe, Takashi Taniguchi, Zhao Liu, Xinghan Cai
Summary: Inelastic electron tunneling (IET) accompanied by energy transfer is widely used to study collective modes in solid-state materials. By directly observing IET in a graphene-based vertical tunnel junction device, characteristic features are linked to phonon-assisted IET, demonstrating a promising method for probing low-energy excitations in graphene-based van der Waals heterostructures.
Article
Chemistry, Physical
Chenjing Quan, Xiao Xing, Tingyuan Jia, Zeyu Zhang, Chunwei Wang, Sihao Huang, Zhengzheng Liu, Juan Du, Yuxin Leng
Summary: The charge transfer process in two-dimensional graphene/transition metal dichalcogenides heterostructures was investigated. The study revealed the correlation between the hot phonon bottleneck effect in graphene and the charge transfer process. The existence of interlayer charge transfer in the heterostructure and its dependence on pump fluence were confirmed.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Review
Chemistry, Multidisciplinary
Shenghan Zhou, Ke Chen, Matthew Thomas Cole, Zhenjun Li, Mo Li, Jun Chen, Christoph Lienau, Chi Li, Qing Dai
Summary: The search for higher frequency information processing has led to intense research in micro, nano, and optoelectronics, with electron tunneling devices offering significantly faster response times compared to conventional semiconductor devices. This enhanced performance is driving the reimagination of traditional electronic devices and the emergence of new lightwave electronics. The current state-of-the-art, challenges, and opportunities in electron tunneling devices are reviewed, alongside potential future research directions in this rapidly advancing field.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Jiang Yao, Peter J. Wagner, Yunpeng Xia, Gregory Czap, W. Ho
Summary: This article introduces the study of DC current generation and its connection with inelastic electron tunneling spectroscopy and microscopy. The research found that although both techniques involve nonlinear features, there are significant differences in line shape analysis, which provides two complementary techniques for probing nanoscale systems.
Article
Chemistry, Multidisciplinary
Xiaoqian Liu, Ran Peng, Zhaoru Sun, Jianpeng Liu
Summary: In this study, the phonon properties of magic-angle twisted bilayer graphene (TBG) were investigated using many-body classical potential and interatomic forces generated by a deep neural network. Various vibrational patterns and their effects on electronic structures were discovered.
Article
Materials Science, Multidisciplinary
Junhyeok Bang, Joongoo Kang
Summary: By opening up intersubband carrier multiplication transitions in nanostructures, the efficiency of carrier multiplication can be significantly enhanced, providing a pathway for developing efficient optoelectronic devices.
Article
Multidisciplinary Sciences
Alexander Kerelsky, Carmen Rubio-Verdu, Lede Xian, Dante M. Kennes, Dorri Halbertal, Nathan Finney, Larry Song, Simon Turkel, Lei Wang, Kenji Watanabe, Takashi Taniguchi, James Hone, Cory Dean, Dmitri N. Basov, Angel Rubio, Abhay N. Pasupathy
Summary: This study demonstrates the formation of emergent correlated phases in multilayer rhombohedral graphene without the need for twisted van der Waals layers. The study shows that two layers of bilayer graphene twisted by a tiny angle can host large regions of uniform rhombohedral four-layer graphene with a sharp van Hove singularity. Furthermore, the study suggests that the broken symmetry state in ABCA graphene could be attributed to a charge-transfer excitonic insulator or a ferrimagnet.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Materials Science, Multidisciplinary
L. Cheng, F. C. Fei, H. Hu, Y. M. Dai, F. Q. Song, J. Qi
Summary: In this study, we used ultrafast optical pump-probe spectroscopy to investigate the quasiparticle dynamics in the type-II Dirac semimetal NiTe2. We observed anomalous dynamic optical responses around the critical temperature T* (-60 K), which were also confirmed by transport experiments. Specifically, our results revealed a phonon-assisted electron-hole recombination process that showed an anomaly at T* <^>' 60 K. We discovered an unusual behavior of phonon renormalization, characterized by anomalies in the temperature-dependent phonon energy and lifetime at T*. We found that these anomalies were due to the sudden shift of the phonon mode involved in the recombination, which was caused by the abrupt change in electronic structure near the Fermi surface. These findings provide deeper insights into the nonequilibrium carrier and lattice properties in topological materials.
Article
Chemistry, Physical
Margarita Tsaousidou, Shrishail S. Kubakaddi
Summary: This paper presents a theoretical model for calculating the energy loss rate (ELR) of hot electrons in monolayer graphene due to their interaction with acoustic phonons at high perpendicular magnetic fields. The ELR is numerically simulated with respect to various factors, such as magnetic field, electron temperature, electron density, and Landau level broadening. The results show oscillations in the ELR due to the oscillating density of states at the Fermi level. The screening effects on the deformation potential coupling are taken into account, leading to a significant reduction in the ELR, especially at low electron temperatures and high magnetic fields.
Article
Chemistry, Multidisciplinary
Manying Liu, Zhenyang Li, Guofeng Wei, Erchuang Fan, Qingli Feng, Dandan Zhao, Yanru Guo, Yange Zhang, Zhi Zheng
Summary: Using the crystalline ECTF film based on the coordination action between pyridinic N and Pb2+, high-quality CsPbBr3@ ECTF-1 films are produced via in situ reaction of PbBr2 and CsBr. These films have fewer grain boundaries, better charge transfer, and superior photoelectron and hole separation compared to pristine CsPbBr3 film.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Chemistry, Physical
Anna Sinterhauf, Georg A. Traeger, Davood Momeni, Klaus Pierz, Hans Werner Schumacher, Martin Wenderoth
Summary: The study reveals that local variations in resistance of graphene on SiC are associated with substrate steps and are intrinsic to the material. The research shows a correlation between step resistance and local conductivity, with step resistance decreasing with increasing conductivity at room temperature and increasing at low temperatures. This behavior is attributed to an interplay between electron-phonon scattering, potential scattering, and charge carrier depletion near the substrate step.
Article
Nanoscience & Nanotechnology
Christian Frydendahl, S. R. K. Chaitanya Indukuri, Meir Grajower, Noa Mazurski, Joseph Shappir, Uriel Levy
Summary: Graphene shows great promise for future applications with easily programmable doping using short gate pulses. This technology can be applied for nonvolatile memory devices and neuromorphic computing, with significant performance enhancement by UV radiation.
Article
Chemistry, Multidisciplinary
Omer Erez-Cohen, Olga Brontvein, Israel Bar-Joseph
Summary: In this study, we investigate electrically driven plasmon (EDP) emission in metal-insulator-semiconductor tunnel junctions. We find that the amorphization of the silicon crystal near the junction due to applied voltage is critical in determining the nature of the emission. We also suggest that the properties of the insulating layer change above a certain voltage threshold, resulting in different spatial properties of EDP emission.
Article
Chemistry, Multidisciplinary
Dmitry Lebedev, Jonathan Tyler Gish, Ethan Skyler Garvey, Teodor Kosev Stanev, Junhwan Choi, Leonidas Georgopoulos, Thomas Wei Song, Hong Youl Park, Kenji Watanabe, Takashi Taniguchi, Nathaniel Patrick Stern, Vinod Kumar Sangwan, Mark Christopher Hersam
Summary: 2D magnetic materials have promising applications in quantum and spintronic devices. 2D antiferromagnetic materials are of interest due to their insensitivity to external magnetic fields and faster switching speeds compared to 2D ferromagnets. However, their lack of macroscopic magnetization hampers the detection and control of antiferromagnetic order, emphasizing the need for magneto-electrical measurements.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Dohun Kim, Byungmin Kang, Yong-Bin Choi, Kenji Watanabe, Takashi Taniguchi, Gil-Ho Lee, Gil Young Cho, Youngwook Kim
Summary: We introduce a novel two-dimensional electronic system called twisted bilayer graphene with a large twist angle, which exhibits ultrastrong interlayer interactions and is ideal for realizing interlayer-coherent excitonic condensates. By fully exploiting the sub-nanometer atomic separation and geometrically suppressed interlayer electron tunneling, we demonstrate the appearance of a sequence of odd-integer quantum Hall states with interlayer coherence at the second Landau level (N = 1). These states have energy gaps of order 1 K, several orders of magnitude greater than those in GaAs. Experimental observations of various quantum Hall phase transitions largely support our phenomenological model calculations. Therefore, we establish the excellent platform of a large twist angle system for high-temperature excitonic condensation.
Article
Nanoscience & Nanotechnology
Ryoichi Kato, Haruki Uchiyama, Tomonori Nishimura, Keiji Ueno, Takashi Taniguchi, Kenji Watanabe, Edward Chen, Kosuke Nagashio
Summary: In this study, high-performance p-type FETs were achieved by selectively applying surface charge-transfer doping from WOx to the access region of WS2 and WSe2. The p-type conversion of intrinsically n-type trilayer WSe2 FET was successfully achieved by reducing the Schottky barrier width and injecting holes into the valence band. However, trilayer WS2 did not show clear p-type conversion due to its lower valence band maximum compared to trilayer WSe2. Using h-BN as a TG insulator, a high-performance p-type WSe2 FET with negligible hysteresis was achieved.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Physics, Applied
Kento Sasaki, Yuki Nakamura, Hao Gu, Moeta Tsukamoto, Shu Nakaharai, Takuya Iwasaki, Kenji Watanabe, Takashi Taniguchi, Shinichi Ogawa, Yukinori Morita, Kensuke Kobayashi
Summary: Placing a sensor close to the target at the nano-level is a central challenge in quantum sensing. We demonstrate magnetic field imaging with a boron vacancy (V-B(-)) defects array in hexagonal boron nitride with a few 10 nm thickness. The sensor array allows us to visualize the magnetic field induced by the current in the straight micro wire with a high spatial resolution. Each sensor exhibits a practical sensitivity of 73.6 mu T/Hz(0.5), suitable for quantum materials research. Our technique of arranging V-B(-) quantum sensors periodically and tightly on measurement targets will maximize their potential.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Martin Endres, Artem Kononov, Hasitha Suriya Arachchige, Jiaqiang Yan, David Mandrus, Kenji Watanabe, Takashi Taniguchi, Christian Schoenenberger
Summary: In this study, we measured a 4N-periodic switching current through an asymmetric SQUID formed by the higher-order topological insulator WTe2. We found that a high asymmetry in critical current and negligible loop inductance alone were not sufficient to reliably measure the current-phase relation. Instead, we discovered that our measurement was heavily influenced by additional inductances originating from the self-formed PdTex inside the junction. We developed a method to numerically recover the current-phase relation and found that the 1.5 μm long junction was best described in the short ballistic limit. Our results highlight the complexity of subtle inductance effects that can lead to misleading topological signatures in transport measurements.
Article
Multidisciplinary Sciences
Wenjin Zhao, Bowen Shen, Zui Tao, Zhongdong Han, Kaifei Kang, Kenji Watanabe, Takashi Taniguchi, Kin Fai Mak, Jie Shan
Summary: Scientists have realized synthetic Kondo lattice in AB-stacked MoTe2/WSe2 moire bilayers, observing heavy fermions and demonstrating gate-tunable Kondo temperatures. This study opens the possibility of accessing the phase diagram of the Kondo lattice using semiconductor moire materials.
Article
Nanoscience & Nanotechnology
Kaifei Kang, Wenjin Zhao, Yihang Zeng, Kenji Watanabe, Takashi Taniguchi, Jie Shan, Kin Fai Mak
Summary: We have achieved the pulsed control of the superlattice effect in two-dimensional materials through the ferroelectric effect, switching between the correlated and superlattice insulating states, and observing the nonlinear anomalous Hall effect. This study demonstrates the potential for creating new functional superlattice materials by incorporating intrinsic symmetry-breaking orders.
NATURE NANOTECHNOLOGY
(2023)
Article
Multidisciplinary Sciences
Richen Xiong, Jacob H. Nie, Samuel L. Brantly, Patrick Hays, Renee Sailus, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Chenhao Jin
Summary: We observe a bosonic correlated insulator composed of excitons in tungsten diselenide/tungsten disulfide (WSe2/WS2) moire superlattices. The insulator transitions continuously into an electron correlated insulator with varying charge density, suggesting a mixed correlated insulating state between the two limits.
Article
Chemistry, Multidisciplinary
Xintong Li, Peng Zhou, Xuan Hu, Ethan Rivers, Kenji Watanabe, Takashi Taniguchi, Deji Akinwande, Joseph S. Friedman, Jean Anne C. Incorvia
Summary: Ambipolar dual-gate transistors based on low-dimensional materials enable reconfigurable logic circuits with suppressed off-state current. This article presents high-performance ambipolar dual-gate transistors based on tungsten diselenide (WSe2), which exhibit high on-off ratio, low off-state current, negligible hysteresis, and ideal subthreshold swing. Cascadable logic gates with minimal static power consumption are demonstrated using these transistors. The study also investigates the behavior of both control gate and polarity gate and analyzes the noise margin and speed performance of the circuits built by dual-gate devices. This work advances the field of ambipolar dual-gate transistors and showcases their potential for low-power, high-speed, and more flexible logic circuits.
Article
Computer Science, Interdisciplinary Applications
Zhenglu Li, Gabriel Antonius, Yang-Hao Chan, Steven G. Louie
Summary: This article presents a workflow for practical calculations of electron-phonon coupling and includes the effect of many-electron correlations using GW perturbation theory. The workflow combines different software packages to enable accurate calculations at the level of quasiparticle band structures.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Chemistry, Multidisciplinary
Hakon Rost, Simon P. Cooil, Anna Cecilie Asland, Jinbang Hu, Ayaz Ali, Takashi Taniguchi, Kenji Watanabe, Branson D. Belle, Bodil Holst, Jerzy T. Sadowski, Federico Mazzola, Justin W. Wells
Summary: Understanding the collective behavior of quasiparticles in solid-state systems is crucial for nonvolatile electronics, allowing control of many-body effects and their applications. Hexagonal boron nitride (hBN) is a wide-energy-bandgap semiconductor with potential for low-dimensional device heterostructures. Despite its inertness, few-layer hBN shows a significant increase in electron mass, affecting the lifetime of pi-band states. The enhancement is phonon-mediated and has important implications for hBN-based devices.
Article
Chemistry, Physical
Lujun Wang, Sotirios Papadopoulos, Fadil Iyikanat, Jian Zhang, Jing Huang, Takashi Taniguchi, Kenji Watanabe, Michel Calame, Mickael L. Perrin, F. Javier Garcia de Abajo, Lukas Novotny
Summary: The authors demonstrate exciton-assisted resonant electron tunnelling in van der Waals heterostructure tunnel junctions. They reveal tunnelling mechanisms involving indirect or direct excitons and optical emission driven by inelastic electron tunnelling. The study highlights the importance of materials with well-defined interfaces and the potential for van der Waals material-based optoelectronic devices.
Article
Multidisciplinary Sciences
Xin Cong, Parisa Ali Mohammadi, Mingyang Zheng, Kenji Watanabe, Takashi Taniguchi, Daniel Rhodes, Xiao-Xiao Zhang
Summary: The study investigates the characteristics of Fermi sea screening on dark excitons in monolayer WSe2 and its correlation with carrier density. The results indicate that the photoluminescence of dark excitons shows distinct p-doping dependence when the carrier density reaches a critical level.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Lei Ren, Cedric Robert, Hanan Dery, Minhao He, Pengke Li, Dinh Van Tuan, Pierre Renucci, Delphine Lagarde, Takashi Taniguchi, Kenji Watanabe, Xiaodong Xu, Xavier Marie
Summary: We investigated charge tunable devices based on WSe2 and WS2 monolayers encapsulated in hexagonal boron nitride. We observed a weaker-intensity optical transition in photoluminescence measurements when the monolayers were electrostatically doped with electrons. Through a detailed characterization of this photoluminescence line, we identified it as an impurity-assisted radiative recombination of the intervalley negatively charged exciton (triplet trion). Our measurements also revealed the spin-orbit splitting energy difference between the emitted photons from the two possible recombination processes of the same triplet trion.
Article
Chemistry, Multidisciplinary
Tien Dat Ngo, Tuyen Huynh, Inyong Moon, Takashi Taniguchi, Kenji Watanabe, Min Sup Choi, Won Jong Yoo
Summary: This study presents a novel approach to overcome the challenges faced by 2D materials in CMOS technology, specifically in the production of high-performance p-type field effect transistors (p-FETs). By fabricating lateral p+-p-p+ junction WSe2 FETs with self-aligned TG stacks and utilizing selective oxygen plasma-doping, the researchers achieve exceptional electrostatic controllability and low power consumption in PMOS inverters.