Two-dimensional (2D) non-van der Waals (vdW) Cr5Te8 has attracted widespread research interest for its air stability and thickness-dependent magnetic properties. However, the growth of large-scale ultrathin 2D Cr5Te8 remains challenging. Here, we selected GaTe powder as the precursor to supply Te monomers and fabricated submillimeter 2D Cr5Te8 nanosheets. By optimizing the growth temperature and source–substrate distance (DSS), we successfully achieved Cr5Te8 nanosheets with a lateral size of up to ∼0.19 mm and corresponding thickness down to ∼4.8 nm. The role of GaTe is to enhance the efficient Te atom concentration, which promotes the lateral growth of Cr5Te8 nanosheets. Furthermore, our findings reveal the appearance of Cr5Te8 nanosheets exhibiting serrated edges and a stacked structure like those of wedding cakes. Magnetic property measurement revealed the intense out-of-plane ferromagnetism in Cr5Te8, with a Curie temperature (TC) of 172 K. This work paves the way for the controllable growth of submillimeter ultrathin 2D ferromagnetic crystals and lays the foundation for the future synthesis of millimeter ultrathin ferromagnets.
Wenjuan Zhao#, Xieyu Zhou#, Dayu Yan#, Yuan Huang*, Cong Li, Qiang Gao, Paolo Moras, Polina M. Sheverdyaeva, Hongtao Rong, Yongqing Cai, Eike F. Schwier, Xixia Zhang, Cheng Shen, Yang Wang, Yu Xu, Wei Ji, Chen Liu, Youguo Shi, Lin Zhao, Lihong Bao, Qingyan Wang, Kenya Shimada, Xutang Tao, Guangyu Zhang, Hongjun Gao, Zuyan Xu, Xingjiang Zhou*, Guodong Liu*
Abstract:
An in-depth understanding of the electronic structure of 2H-MoTe2 at the atomic layer limit is a crucial step towards its exploitation in nanoscale devices. Here, we show that millimeter-sized monolayer (ML) MoTe2 samples, as well as smaller sized bilayer (BL) samples, can be obtained using the mechanical exfoliation technique. The electronic structure of these materials is investigated by Angle-Resolved Photoemission Spectroscopy (ARPES) for the first time and Density Functional Theory (DFT) calculations. The comparison between experiments and theory allows us to describe ML MoTe2 as a semiconductor with direct gap at K point. This scenario is reinforced by the experimental observation of the conduction band minimum at K in Rb-doped ML MoTe2, resulting in a gap of at least 0.924 eV. In the BL MoTe2 system the maxima of the bands at Γ and K display very similar energies, thus leaving the door open to a direct gap scenario, in analogy to WSe2. The monotonic increase in the separation between spin-split bands at K while moving from ML to BL and bulk-like MoTe2 is attributed to interlayer coupling. Our findings can be considered as a reference to understand Quantum Anomalous and Fractional Quantum Anomalous Hall Effects recently discovered in ML and BL MoTe2 based moir´ e heterostructures.
Renhong Wang (王人宏), Cong Wang (王聪)*, Ruixuan Li (李睿宣), Deping Guo (郭的坪), Jiaqi Dai (戴佳琦), Canbo Zong (宗灿波), Weihan Zhang (张伟 涵), and Wei Ji (季威)*
Abstract:
Kagome materials are known for hosting exotic quantum states, including quantum spin liquids, charge density waves, and unconventional superconductivity. The search for kagome monolayers is driven by their ability to exhibit neat and well-defined kagome bands near the Fermi level, which are more easily realized in the absence of interlayer interactions. However, this absence also destabilizes the monolayer forms of many bulk kagome materials, posing significant challenges to their discovery. In this work, we propose a strategy to address this challenge by utilizing oxygen vacancies in transition metal oxides within a “1+3” design framework. Through high-throughput computational screening of 349 candidate materials, we identified 12 thermodynamically stable kagome monolayers with diverse electronic and magnetic properties. These materials were classified into three categories based on their lattice geometry, symmetry, band gaps, and magnetic configurations. Detailed analysis of three representative monolayers revealed kagome band features near their Fermi levels, with orbital contributions varying between oxygen 2p and transition metal d states. This study demonstrates the feasibility of the “1+3” strategy, offering a promising approach to uncovering low-dimensional kagome materials and advancing the exploration of their quantum phenomena.
Yanyan Geng+, Haoyu Dong+, Renhong Wang+, Jianfeng Guo, Shuo Mi, Le Lei, Yan Li, Li Huang, Fei Pang, Rui Xu, Weiqiang Yu, Hong-Jun Gao, Wei Ji*, Weichang Zhou*, and Zhihai Cheng*
Abstract:
The delicate interplay among the complex intra-/inter-layer electron-electron and electron-lattice interactions is the fundamental prerequisite of these exotic quantum states, such as superconductivity, nematic order, and checkerboard charge order. Here we explore the filling-dependent multiple stable intertwined electronic and atomic orders of flat-band state of 1T-TaS2 encompassing hole order, phase orders, coexisting left- and right-chiral orders and mixed phase/chiral orders via scanning tunneling microscopy (STM). Combining first principles calculations, the novel emergent electronic/ atomic orders can be attributed to the weakening of electron-electron correlations and stacking-dependent interlayer interactions. Moreover, achiral intermediate ring-like clusters and nematic charge density wave (CDW) states are successfully realized in intralayer chiral domain wall and interlayer heterochiral stacking regions through chiral overlap configurations. Our study not only deepens the understanding of filling-dependent electronic/atomic orders in flat-band systems, but also offers new perspectives for exploring exotic quantum states in correlated electronic systems.
Zhongqin Zhang† , Jiaqi Dai† , Cong Wang , Hua Zhu , Fei Pang , Zhihai Cheng, and Wei Ji*
Abstract:
In recent years, kagome materials have attracted significant attention due to their rich emergent phenomena arising from the quantum interplay of geometry, topology, spin, and correlations. However, in the search for kagome materials, it has been found that bulk compounds with electronic properties related to the kagome lattice are relatively scarce, primarily due to the hybridization of kagome layers with adjacent layers. Therefore, researchers have shown increasing interest in the discovery and construction of two-dimensional (2D) kagome materials, aiming to achieve clean kagome bands near the Fermi level in monolayer or few-layer systems. Substantial advancements have already been made in this area. In this review, we summarize the current progress in the construction and development of 2D kagome materials. We begin by introducing the geometric and electronic structures of the kagome lattice model and its variants, followed by discussions on the experimental realizations and electronic structure characterizations of 2D kagome materials. Finally, we provide an outlook on the future developments of 2D kagome materials.
