Article
Nanoscience & Nanotechnology
Guilliam Butseraen, Arpit Ranadive, Nicolas Aparicio, Kazi Rafsanjani Amin, Abhishek Juyal, Martina Esposito, Kenji Watanabe, Takashi Taniguchi, Nicolas Roch, Francois Lefloch, Julien Renard
Summary: This study demonstrates a tunable parametric amplifier using a graphene Josephson junction, with the ability to tune its working frequency widely through gate voltage. The amplifier exhibits a gain exceeding 20 dB and noise performance close to the standard quantum limit. These findings expand the toolset for electrically tunable superconducting quantum circuits and offer opportunities for the development of quantum technologies such as quantum computing and quantum sensing, as well as for fundamental science.
NATURE NANOTECHNOLOGY
(2022)
Editorial Material
Nanoscience & Nanotechnology
Jonathan R. Prance, Moshe Ben Shalom
Summary: Twisted bilayer graphene allows for the creation of Josephson junctions and single electron transistors in a single, crystalline material using only electric field gating, thus eliminating the need for interfaces between different materials.
NATURE NANOTECHNOLOGY
(2021)
Article
Nanoscience & Nanotechnology
Folkert K. de Vries, Elias Portoles, Giulia Zheng, Takashi Taniguchi, Kenji Watanabe, Thomas Ihn, Klaus Ensslin, Peter Rickhaus
Summary: Magic-angle twisted bilayer graphene (MATBG) has emerged as a versatile platform combining metallic, superconducting, magnetic, and insulating phases in a single crystal. By using multilayer gate technology, this study successfully created devices based on two distinct phases in adjustable regions of MATBG and observed tunable Josephson effects.
NATURE NANOTECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
John Chiles, Ethan G. Arnault, Chun-Chia Chen, Trevyn F. Q. Larson, Lingfei Zhao, Kenji Watanabe, Takashi Taniguchi, Francois Amet, Gleb Finkelstein
Summary: This article introduces a device using superconducting diodes as non-reciprocal circuit elements, which enables non-dissipative transport in one direction and resistive transport in the opposite direction. The device consists of three graphene Josephson junctions connected by a common superconducting island, referred to as a Josephson triode. By breaking the time-reversal symmetry with a control current, the device achieves efficiencies approaching 100% without the need for a magnetic field. The utility of the triode is demonstrated by rectifying a small amplitude square wave, indicating its potential application in modern quantum circuits.
Article
Materials Science, Multidisciplinary
Ayush Singh, Colin Benjamin
Summary: The research team designed a highly efficient quantum Otto engine using twisted bilayer graphene, and found that the maximum power output efficiency occurs at the magic angle, potentially advancing the performance of nanoscale devices.
Article
Multidisciplinary Sciences
Jeong Min Park, Yuan Cao, Kenji Watanabe, Takashi Taniguchi, Pablo Jarillo-Herrero
Summary: Moire superlattices have become a platform for studying correlated physics and superconductivity with unprecedented tunability. This study on magic-angle twisted trilayer graphene reveals a better tunability of electronic structure and superconducting properties than magic-angle twisted bilayer graphene, with implications for the understanding of strongly coupled superconductivity. The results suggest that the system can be electrically tuned close to the crossover to a two-dimensional Bose-Einstein condensate, indicating the potential for revolutionizing applications of superconductivity.
Article
Materials Science, Multidisciplinary
Tom Dvir, Ayelet Zalic, Eirik Holm Fyhn, Morten Amundsen, Takashi Taniguchi, Kenji Watanabe, Jacob Linder, Hadar Steinberg
Summary: Researchers utilized thin NbSe2 as superconducting electrodes laterally coupled to graphene to form a planar van der Waals two-dimensional Josephson junction. By studying the behavior of these novel devices with respect to temperature, gate voltage, and magnetic fields, they found that the junctions could sustain supercurrent up to high parallel magnetic fields of 8.5 T.
Article
Physics, Multidisciplinary
Massimiliano Lucci, Davide Cassi, Vittorio Merlo, Roberto Russo, Gaetano Salina, Matteo Cirillo
Summary: Evidence suggests that topological effects in graph-shaped arrays of superconducting islands can influence superconducting energy gap and transition temperature. The new phase is generated by pairs of electrons (Cooper pairs) behaving as bosons in the superconducting state. The coupling between the islands is provided by Josephson junctions, and the distribution on the islands is probed by a unique technique that allows for boson hopping between the islands.
Article
Multidisciplinary Sciences
J. Diez-Merida, A. Diez-Carlon, S. Y. Yang, Y. -M. Xie, X. -J. Gao, J. Senior, K. Watanabe, T. Taniguchi, X. Lu, A. P. Higginbotham, K. T. Law, Dmitri K. Efetov
Summary: The authors demonstrate a Josephson junction in magic-angle twisted bilayer graphene with a correlated insulator weak link, showing magnetism and programmable superconducting diode behavior. The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation of hybrid Josephson junctions.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Asaf Rozen, Jeong Min Park, Uri Zondiner, Yuan Cao, Daniel Rodan-Legrain, Takashi Taniguchi, Kenji Watanabe, Yuval Oreg, Ady Stern, Erez Berg, Pablo Jarillo-Herrero, Shahal Ilani
Summary: The study reveals a transition from a low-entropy electronic liquid to a high-entropy correlated state in magic-angle twisted bilayer graphene under the influence of electron density, temperature, and magnetic field. The correlated state demonstrates a unique combination of properties associated with itinerant electrons and localized moments, with distinct energy scales for different characteristics. The hybrid nature of the correlated state and the separation of energy scales have significant implications for the thermodynamic and transport properties of twisted bilayer graphene.
Article
Multidisciplinary Sciences
Zeyu Hao, A. M. Zimmerman, Patrick Ledwith, Eslam Khalaf, Danial Haie Najafabadi, Kenji Watanabe, Takashi Taniguchi, Ashvin Vishwanath, Philip Kim
Summary: By constructing a van der Waals heterostructure with three stacked graphene layers at alternating twist angles, researchers observed tunable superconductivity at a specific twist angle. The superconducting regions are associated with flavor polarization of moire bands and are bounded by a van Hove singularity at high displacement fields, indicating unconventional moire superconductivity.
Article
Multidisciplinary Sciences
Yonglong Xie, Andrew T. Pierce, Jeong Min Park, Daniel E. Parker, Eslam Khalaf, Patrick Ledwith, Yuan Cao, Seung Hwan Lee, Shaowen Chen, Patrick R. Forrester, Kenji Watanabe, Takashi Taniguchi, Ashvin Vishwanath, Pablo Jarillo-Herrero, Amir Yacoby
Summary: Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states and have been recently observed in magic-angle twisted BLG at low magnetic field. The appearance of these states at 5 T is accompanied by the disappearance of nearby topologically trivial charge density wave states.
Article
Multidisciplinary Sciences
Youngjoon Choi, Hyunjin Kim, Yang Peng, Alex Thomson, Cyprian Lewandowski, Robert Polski, Yiran Zhang, Harpreet Singh Arora, Kenji Watanabe, Takashi Taniguchi, Jason Alicea, Stevan Nadj-Perge
Summary: Magic-angle twisted bilayer graphene (MATBG) exhibits a variety of correlated phenomena, and new techniques introduced can determine the topological phases that emerge in MATBG in a finite magnetic field. These topological phases form only in a specific range of twist angles and are influenced by strong electronic interactions.
Article
Physics, Multidisciplinary
Ya-Ning Ren, Yu -Chen Zhuang, Qing-Feng Sun, Lin He
Summary: Combining inhomogeneous pseudomagnetic fields in strained graphene with real magnetic fields can result in valley-contrasting spatial confinement and yield field-tunable valley-polarized confined states. This provides a new approach to manipulate the valley degree of freedom.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Michael Barth, Jacob Fuchs, Denis Kochan
Summary: This study investigates the interplay between spectral and transport properties in bilayer graphene and s-wave superconductors using Green's function analytical methods and numerical simulations. The results reveal unique superconducting signatures that differentiate between resonant and off-resonant regimes, providing important insights into the behavior of bilayer graphene and other functionalized superconductors.
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)
