Article
Chemistry, Multidisciplinary
Tongyao Zhang, Siwen Zhao, Anran Wang, Zhiren Xiong, Yingjia Liu, Ming Xi, Songlin Li, Hechang Lei, Zheng Vitto Han, Fengqiu Wang
Summary: By contacting a monolayer MoSe2 with a 2D ferromagnetic semiconductor, researchers have successfully manipulated the valley-polarization of MoSe2 and fabricated a spin functional device with both electrical and magnetic tunability. This study provides new insights into the manipulation of valley-polarization and represents an important step forward in the development of field-controlled 2D magneto-optoelectronic devices.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Optics
Garima Gupta, Kenji Watanabe, Takashi Taniguchi, Kausik Majumdar
Summary: In monolayer transition metal dichalcogenide semiconductors, valley coherence degrades rapidly due to scattering and inter-valley exchange interaction. However, by using a sandwich structure of monolayer MoS2 between top and bottom graphene, fully valley-coherent excitons with high degree of linear polarization are achieved. This is attributed to the suppression in exchange interaction, reduction in exciton lifetime, and operating in the motional narrowing regime.
LIGHT-SCIENCE & APPLICATIONS
(2023)
Article
Nanoscience & Nanotechnology
Lei Huang, Xiaofan Zhu, Guohua Hu, Chunyu Deng, Yu Sun, Dongyu Wang, Mengjia Lu, Binfeng Yun, Ruohu Zhang, Yan Zhang, Yiping Cui
Summary: This study demonstrates the electrical switching of room-temperature valley polarization at off-resonance wavelength through a gate-tunable double-resonance chiral micro-structure. It enriches the functions of TMDs-based optoelectronic devices and may have important applications in future valley-polarized encode and information processing devices.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Fabio Caruso, Maximilian Schebek, Yiming Pan, Cecilia Vona, Claudia Draxl
Summary: By controlling the valley degrees of freedom in transition-metal dichalcogenides, valley-selective circular dichroism has become a key concept in valleytronics. It has been discovered that valley excitons, bound electron-hole pairs formed at specific valleys upon absorption of circularly polarized light, are chiral quasiparticles characterized by a finite orbital angular momentum. Additionally, these excitons exhibit a finite magnetization and undergo an excitonic Zeeman splitting when interacting with external magnetic fields.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Optics
Haiyang Liu, Xuanli Zheng, Gaohong Liu, Jun Yin, Congming Ke, Weihuang Yang, Yaping Wu, Zhiming Wu, Xu Li, Chunmiao Zhang, Feiya Xu, Junyong Kang
Summary: A phase engineering strategy aided by resonant plasmonic coupling is proposed to manipulate the valley degree of freedom in transition metal dichalcogenides. Through the designed plasmonic array, the hybrid phase WSe2 exhibits enhanced circular polarization and valley polarization. Finite difference time domain simulations demonstrate consistent polarization effects between theory and experiment. The high polarizations are attributed to increased exciton generation and radiation efficiency, chiral electromagnetic field, and non-equilibrium spin distribution in the hybrid phase.
LASER & PHOTONICS REVIEWS
(2023)
Article
Chemistry, Physical
Wenzhe Zhou, Liang Wu, Aolin Li, Bei Zhang, Fangping Ouyang
Summary: The study demonstrates the spin-orbit coupling and valley-related properties of the monolayer WSi2N4 family, showing that changing the stacking can result in a Rashba spin-orbit field for controlling the spin direction of electrons. The characteristics of a Rashba semiconductor can be utilized for spin/valley Hall effects and manipulation of multiple degrees of freedom of electrons in monolayer materials.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Yan Zhang, Keisuke Shinokita, Kenji Watanabe, Takashi Taniguchi, Yuhei Miyauchi, Kazunari Matsuda
Summary: The study investigates the valley polarization dynamics of excitonic states in MoSe2 under strong magnetic field, attributing the induced valley polarizations to the asymmetric valley scattering of trions due to the valley Zeeman effect under magnetic field. The feeding of valley-polarized excitons for trions formation and longer inter-valley scattering time contribute to the larger valley polarization of trions than that of excitons in 1L-MoSe2.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Physics, Multidisciplinary
Pasquale Cilibrizzi, Xiaoze Liu, Peiyao Zhang, Chenzhe Wang, Quanwei Li, Sui Yang, Xiang Zhang
Summary: The newly discovered valley degree of freedom in atomically thin two-dimensional transition metal dichalcogenides presents an exciting opportunity to explore nonlinear physics phenomena. However, the critical nonlinearity effect, including valley polariton bosonic stimulation, has been a challenge to achieve. In this study, we demonstrate the self-induced valley bosonic stimulation of exciton polaritons in a WS2 monolayer microcavity through resonant injection of valley polaritons at specific energy and wave vector. This finding opens up possibilities for investigating spin ordering and phase transitions, as well as the realization of polariton spin lattices in moire polariton systems and spin lasers.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Applied
T. Ji, Q. Chen, B. C. Ren, Y. Guo, R. Y. Yuan
Summary: In this paper, an asymmetric monolayer WSe2 electrical quantum structure is proposed for investigating the optically controlled valley transport properties. It is found that perfect valley polarization can be achieved with both homo-chiral and anti-chiral off-resonant circularly polarized lights. The valley-polarized conductance presents resonant phenomenon when anti-chiral lights are radiated, and the resonance can be modulated by the intensity of gate voltage, incident energy and angle.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Yinzhou Yan, Xiaohua Zhang, Xiaoze Li, Honghua Fang, Yijian Jiang, Chen Zhao
Summary: A novel design is proposed to significantly enhance the degree of valley polarization (DoP) in ML-WSe2 by introducing Purcell effect and nanofocusing effect through a microsphere cavity array. The Purcell effect in the microcavity enhances the radiative decay rate, locking more polarized excitons in the corresponding valley. The nanofocusing effect increases the number of charged excitons by suppressing bright to dark exciton conversion. This study achieves a high DoP in ML-WSe2 with a simple configuration, promising broad applications in valleytronic devices and chiral optics in the future.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Chen Yang, Zhigang Song, Xiaotian Sun, Jing Lu
Summary: This study predicts that monolayer MoSi2N4 and its derivative MoSi2As4 may exhibit valley-contrasting properties that can be described by a three-band low-power Hamiltonian. These materials have the potential applications in valleytronic devices, especially in multiple information processing, marking a theoretical advance in the field.
Article
Physics, Multidisciplinary
T. Smolenski, K. Watanabe, T. Taniguchi, M. Kroner, A. Imamoglu
Summary: In this study, we investigate the relaxation dynamics of a strongly correlated electron system in a gate-tunable MoSe2 monolayer exposed to a strong magnetic field. We find that the relaxation and light-induced depolarization rates exhibit different behaviors at different Landau level filling factors. Our findings reveal the potential of spin-valley dynamics in probing the effects of disorder and strong interactions.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Xiangyu Feng, Xilong Xu, Zhonglin He, Rui Peng, Ying Dai, Baibiao Huang, Yandong Ma
Summary: Single-layer VSi2P4 demonstrates valley-related multiple Hall effect and spontaneous valley polarization. Under external strain, it can exhibit the long-sought valley-polarized quantum anomalous Hall effect.
Article
Chemistry, Physical
J. J. Lu, R. Liu, F. F. Yue, X. W. Zhao, G. C. Hu, X. B. Yuan, J. F. Ren
Summary: Through first-principles calculations, we have discovered a two-dimensional MXene material, Y3N2O2, with spontaneous valley polarization (VP) that induces intrinsic anomalous valley Hall effect (AVHE). The VP can be linearly modulated, providing an effective control route for valley signals. By adjusting spin-orbit coupling, we have enhanced the VP in the proposed monolayer La3N2O2 to 100.4 meV, enabling easy achievement of AVHE. This work not only offers compelling AVHE material candidates but also presents a novel mindset for finding suitable valleytronic devices.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Materials Science, Multidisciplinary
San-Dong Guo, Yu -Ling Tao, Hao-Tian Guo, Zhuo-Yan Zhao, Bing Wang, Guangzhao Wang, Xiaotian Wang
Summary: This study proposes the concept of quasi-half-valley metals (QHVM) and illustrates it using the example of a VGe2P4 monolayer through first-principle calculations. By tuning the valley properties of VGe2P4 in an electric field, the QHVM can be better realized and its polarization properties can be effectively controlled. This research paves the way for the design of two-dimensional functional materials for valleytronics.
Review
Multidisciplinary Sciences
Chun Ning Lau, Marc W. Bockrath, Kin Fai Mak, Fan Zhang
Summary: Overlaying two atomic layers with a slight lattice mismatch or at a small rotation angle creates a moire superlattice, which has properties that are markedly modified from (and at times entirely absent in) the 'parent' materials. Moire materials have advanced the study and engineering of strongly correlated phenomena and topological systems in reduced dimensions. Understanding electronic phases like superconductivity necessitates precise control in fabrication, involving the rotational alignment of two atomically thin layers with high angular precision.
Article
Nanoscience & Nanotechnology
Yang Xu, Ariana Ray, Yu-Tsun Shao, Shengwei Jiang, Kihong Lee, Daniel Weber, Joshua E. Goldberger, Kenji Watanabe, Takashi Taniguchi, David A. Muller, Kin Fai Mak, Jie Shan
Summary: Research on Moire engineering in van der Waals magnetic materials has shown the potential to create new magnetic ground states, with experiments showcasing the coexistence of ferromagnetic and antiferromagnetic states in small-twist-angle CrI3 bilayers, which can be controlled by electric gating.
NATURE NANOTECHNOLOGY
(2022)
Article
Physics, Multidisciplinary
Ying-Ming Xie, Cheng-Ping Zhang, Jin-Xin Hu, Kin Fai Mak, K. T. Law
Summary: Moire heterobilayer transition metal dichalcogenides (TMDs) are ideal for simulating the single-band Hubbard model and interesting correlated phases have been observed in these systems. Recent research has shown that topologically nontrivial states can be observed in heterobilayers, in which pseudomagnetic fields induced by lattice relaxation play a crucial role.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Jie Gu, Liguo Ma, Song Liu, Kenji Watanabe, Takashi Taniguchi, James C. Hone, Jie Shan, Kin Fai Mak
Summary: This study observes a correlated dipolar excitonic insulator and realizes a charge-insulating state driven by exciton formation in moire materials. Previous experimental studies have mainly focused on correlated electronic states. The results show that correlated quantum phenomena described by bosonic lattice models can be achieved in solid-state systems.
Article
Multidisciplinary Sciences
Saien Xie, Brendan D. Faeth, Yanhao Tang, Lizhong Li, Eli Gerber, Christopher T. Parzyck, Debanjan Chowdhury, Ya-Hui Zhang, Christopher Jozwiak, Aaron Bostwick, Eli Rotenberg, Eun-Ah Kim, Jie Shan, Kin Fai Mak, Kyle M. Shen
Summary: By studying WS2/WSe2 moire superlattices and graphene/WS2/WSe2 trilayer heterostructures, we discovered that the hybridization of moire bands in WS2/WSe2 exhibits an unusually large momentum dependence, and the same WS2/WSe2 superlattice can imprint an unexpectedly large moire potential on a separate layer of graphene.
Article
Chemistry, Multidisciplinary
Kaifei Kang, Helmuth Berger, Kenji Watanabe, Takashi Taniguchi, Laszlo Forro, Jie Shan, Kin Fai Mak
Summary: Researchers have observed a thickness-driven 0-pi transition in Josephson junctions made of NbSe2 and Cr2Ge2Te6, and have also observed unusual supercurrent interference patterns near the critical thickness, indicating the formation of nanoscale domains in Cr2Ge2Te6.
Review
Nanoscience & Nanotechnology
Kin Fai Mak, Jie Shan
Summary: This article elaborates on the recent developments and future opportunities and challenges in fundamental research on semiconductor moire materials, with a particular focus on transition metal dichalcogenides.
NATURE NANOTECHNOLOGY
(2022)
Article
Nanoscience & Nanotechnology
Yang Xu, Kaifei Kang, Kenji Watanabe, Takashi Taniguchi, Kin Fai Mak, Jie Shan
Summary: Twisting the AB-homobilayer of WSe2 enables the realization of bilayer Hubbard model in the weak interlayer hopping limit, leading to observation of competing electronic states transition.
NATURE NANOTECHNOLOGY
(2022)
Article
Multidisciplinary Sciences
Yanhao Tang, Jie Gu, Song Liu, Kenji Watanabe, Takashi Taniguchi, James C. Hone, Kin Fai Mak, Jie Shan
Summary: The study demonstrates the bandwidth-tuned metal-insulator transition in a MoSe2/WS2 moire superlattice and presents evidence for the continuous Wigner-Mott transition. The transition is accompanied by a diverging dielectric constant, indicating a 'dielectric catastrophe' driven by critical charge dynamics. These findings stimulate future explorations of exotic quantum phases in two-dimensional triangular lattices.
NATURE COMMUNICATIONS
(2022)
Editorial Material
Nanoscience & Nanotechnology
Matthew Yankowitz, Kin Fai Mak
Article
Chemistry, Physical
Yihang Zeng, Zhengchao Xia, Roei Dery, Kenji Watanabe, Takashi Taniguchi, Jie Shan, Kin Fai Mak
Summary: In a heterostructure composed of WS2/bilayer WSe2/WS2 multilayers, it was discovered that strongly correlated bosons can be trapped in a triangular lattice. Correlated insulating states were observed when the electron filling factor of the two lattices reached 1/3, 2/3, 4/3, and 5/3. These states can be explained as exciton density waves in a Bose-Fermi mixture of excitons and holes. The strong repulsive interactions between the constituents led to the formation of robust generalized Wigner crystals, which restricted the exciton fluid to channels that spontaneously broke the translational symmetry of the lattice. These results demonstrate that Coulomb-coupled lattices are a fertile ground for studying correlated many-boson phenomena.
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
Physics, Multidisciplinary
C. L. Tschirhart, Evgeny Redekop, Lizhong Li, Tingxin Li, Shengwei Jiang, T. Arp, O. Sheekey, Takashi Taniguchi, Kenji Watanabe, M. E. Huber, Kin Fai Mak, Jie Shan, A. F. Young
Summary: Magnetic switching via spin-orbit torque is demonstrated in a moire bilayer, providing a platform for spintronic applications.
