Kuakua Lu#, Yun Li#,*, Qijing Wang#,* Linlu Wu#, Xinglong Ren, Xu Chen, Luhao Liu, Yating Li, Xiaoming Xu, Qingkai Zhang, Di Wang, Liqi Zhou, Mingfei Xiao, Sai Jiang, Mengjiao Pei, Haoxin Gong, William Wood, Ian E. Jacobs, Junzhan Wang, Gang Chen, Peng Wang, Zhaosheng Li, Chunfeng Zhang, Xinran Wang, Xu Wu, Yeliang Wang, Wei Ji, Songlin Li, Jingsi Qiao*, Yi Shi*, Henning Sirringhaus*
Abstract:
Metallic charge transport of field-induced carriers can be observed in single-crystal silicon over a wide temperature range. Such behaviour is rare in undoped organic semiconductors but is beneficial for engineering devices with advanced performance. Here we report metallic charge transport in conjugated molecular bilayers down to 8 K with an electrical conductivity of up to 245 S cm−1 and a Hall mobility larger than 100 cm2 V−1 s−1 at 20 K. We use molecular-crystal bilayers of the organic semiconductor 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene. We infer that this transport behaviour originates from the phenyl bridge coupling between the two molecular layers, which suppresses molecular vibrations and weakens Coulomb interactions. We develop a controlled method for introducing defects, using which we observe a disorder-driven metal–insulator transition in the molecular crystal.
The integration of electronic and photonic chips hinges on the availability of efficient light sources and modulators that are compatible with on-chip interconnects. Among these, mid-infrared (mid-IR) emitters are especially critical, as they enable low-loss transmission through atmospheric windows and unlock powerful capabilities for molecular fingerprinting and chemical sensing. In this study, we demonstrate that 2D tellurium (Te) nanoflakes can serve as highly efficient, electrically tunable, and linearly polarized mid-IR emitters. Leveraging the narrow direct bandgap (≈0.36 eV) and anisotropic crystal symmetry of Te nanoflakes, we achieve electrically tunable mid-IR photoluminescence (PL) with near-complete PL intensity modulation, a stable emission wavelength (≈3.4 µm), and near-perfect linear polarization. In addition, we demonstrate a dual-gate device that allows independent control of the electrostatic doping and vertical electric field, and further theoretical analysis reveals that the electrical tunability of the PL intensity originates primarily from the gate-controlled carrier density. Building on this robust control, we demonstrate high-speed electro-optical switches and programmable logic gates for on-chip encryption, underscoring the excellent compatibility of Te with advanced optoelectronic circuits. Collectively, these advances establish Te as a cornerstone material for hybrid electronic-photonic systems, directly addressing the urgent demand for mid-IR components in next-generation optical interconnects.
Mao-Peng Miao, Nanshu Liu, Wen-Hao Zhang, Jian-Wang Zhou, Dao-Bo Wang, Cong Wang, Wei Ji, and Ying-Shuang Fu
Abstract:
Noncollinear magnetic orders in monolayer van der Waals magnets are crucial for probing delicate magnetic interactions under minimal spatial constraints and advancing miniaturized spintronic devices. Despite their significance, achieving atomic-scale identification remains challenging. In this study, we utilized spin-polarized scanning tunneling microscopy and density functional theory calculations to identify spin-spiral orders in mono- and bi-layer NiI2, grown on graphene-covered SiC(0001) substrates. We discovered two distinct spin-spiral states with Q vectors aligning and deviating by 7° from the lattice direction, exhibiting periodicities of 4.54 and 5.01 times the lattice constant, respectively. These findings contrast with bulk properties and align closely with our theoretical predictions. Surprisingly, the finite sizes of monolayers induce incommensurability with the spin-spiral period, facilitating collective spin switching behavior under magnetic fields. Our research reveals intrinsic noncollinear magnetism at the monolayer limit with unprecedented resolution, paving the way for exploring novel spin phenomena.
Shuo Mi#, Manyu Wang#, Bingxian Shi#, Songyang Li, Xiaoxiao Pei, Yanyan Geng, Shumin Meng, Rui Xu, Li Huang, Wei Ji, Fei Pang, Peng Cheng*, Jianfeng Guo*, and Zhihai Cheng*
Abstract:
Strain engineering offers a compelling route to modulate magnetism in two-dimensional (2D) materials, yet most approaches rely on externally applied strain. An in-plane anisotropic 2D-layered ferromagnet FePd2Te2 provides a suitable platform to study intrinsic strain-magnetism coupling due to its twinning domains. Here, we report spatially modulated internal compressive/tensile(C/T) strain regions in FePd2Te2 and their strong impact on local magnetic properties in real space by using atomic/magnetic force microscopy (AFM/MFM) combined with scanning tunneling microscopy (STM). Field- and strain-dependent spin transformations reveal the modulation of its intrinsic C/T regions. Notably, C regions retain intact Fe zigzag chains and exhibit larger, abruptly switching magnetic moments, while T regions display fragmented chains with reduced, gradually rotating spins. The intrinsic strain-induced intact ferromagnetic (FM), field-induced polarized-FM states, and their transitions are comparatively discussed during magnetic measurements. Temperature- and field-dependent evolution are further investigated in the FM and paramagnetic (PM) states and summarized to obtain an H-T phase diagram of FePd2Te2. Our work provides key results for understanding real-space tunable magnetic states through internal structural heterogeneity and suggests potential strategies for manipulating intrinsic strain-engineered magnetic devices.
Xiaoqing Chen#, Huijuan Zhao#, Ruixiang Fei, Chun Huang, Jingsi Qiao, Cheng Sun, Haiming Zhu, Li Zhan, Zehua Hu, Songlin Li, Li Yang, Zemin Tang, Lianhui Wang, Yi Shi, Wei Ji, Jian-Bin Xu, Li Gao*, Xuetao Gan* & Xinran Wang*
Abstract:
Two-dimensional (2D) materials offer strong light-matter interaction and design flexibility beyond bulk semiconductors, but an intrinsic limit is the low absorption imposed by the atomic thickness. A long-sought-after goal is to achieve complementary absorption enhancement through energy transfer (ET) to break this limit. However, it is found challenging due to the competing charge transfer (CT) process and lack of resonance in exciton states. Here, we report highly efficient ET in a 2D hybrid organic-inorganic heterostructure (HOIST) of Me-PTCDI/WS2. Resonant ET is observed leading to enhanced WS2 photoluminescence (PL) by 124 times. We identify Dexter exchange between the Frenkel state in donor and an excited 2s state in acceptor as the main ET mechanism, as supported by density functional theory calculations. We further demonstrate ET-enhanced phototransistor devices with enhanced responsivity by nearly 1000 times without sacrificing the response time. Our results expand the understanding of interlayer relaxation processes in 2D materials and open opportunities in optoelectronic devices.
