Atomically thin transition metal dichalcogenides exhibit strong excitonic effects and rich light-matter interactions, yet active control over their optical near-field response remains challenging. Here, we demonstrate an intercalation-enabled strategy to tune the near-field response of MoS2 through electrochemical insertion of tetraethylammonium ions. The resulting (TEA)xMoS2 exhibits a markedly expanded interlayer spacing (12.17 & Aring;) and substantial reconstruction of its electronic, dielectric, and excitonic properties. Steady-state and ultrafast spectroscopy reveal redshifted and intensified excitonic resonances, a more pronounced monolayer-like emission response, and prolonged excitonic bleach dynamics after intercalation. Consistently, nano-optical imaging shows a substantially enhanced near-field response. Combined optical analyses support an intercalation-modified exciton-coupled near-field mode rather than a conventional plasmonic origin. Consequently, (TEA)xMoS2 enables molecular detection down to 10-9 m, establishing electrochemical intercalation as a practical route for excitonic near-field engineering in van der Waals semiconductors.

The effects of Co doping in a series of La3Ni2-xCoxO7-delta samples before and after high oxygen pressure annealing have been investigated. The structural refinements suggest that the Co ions could be incorporated into the La3Ni2O7-delta matrix with a high solution level of x = 0.3. Despite of substantial increase in electrical conductivity with increasing Co doping, the as-prepared La3Ni2-xCoxO7-delta samples exhibit insulator-like conductivity. Noticeably, the high oxygen pressure annealing treatment results in an increase in the oxygen content and the average valence state of Ni ions of the La3Ni2-xCoxO7-delta samples. As a result, the annealed La3Ni2-xCoxO7-delta samples exhibit an insulator-to-metal transition, and the metallic-like conductivity could be achieved above similar to 20 K in Co-doped samples.

The suppression of density wave in bilayer nickelate La3Ni2O7 under pressure has been identified as a critical factor enabling pressure-induced high-temperature superconductivity. However, this density wave state exhibits remarkable stability against most alternative tuning methods except the high-pressure technique. Herein through systematic investigations of Tb doping effects on electrical transport and magnetic properties, we observe a gradual suppression of density wave transition temperature with the increasing Tb concentration, accompanied by the emergence of negative magnetoresistance persisting up to 14 T. Magnetic susceptibility measurements further reveal the formation of a doping-induced spin-glass state, which likely accounts for the observed negative magnetoresistance phenomenon. This work establishes an effective chemical doping approach to manipulate the density wave state and correlated quantum state in La3Ni2O7, offering new insights into the mechanism of hightemperature superconductivity and potential pathways toward achieving ambient-pressure superconductivity in bulk nickelate crystals.

Bismuth-based chalcohalides are emerging as a promising family of materials for optoelectronics due to their intrinsically anisotropic optical and electronic properties. However, the lack of high-quality crystals has hindered access to their intrinsic physical properties. Here, we present the synthesis and comprehensive optoelectronic characterization of quasi-one-dimensional (1D) van der Waals (vdW) BiSeBr crystals. This work establishes a previously unreported synergy, the coexistence of ferroelectricity and self-trapped excitons (STEs) in a single quasi-1D semiconductor, and its exploitation for multifunctional polarization-sensitive photodetection. The low-dimensional chain structure of BiSeBr breaks inversion symmetry, giving rise to out-of-plane ferroelectric behavior and a second-harmonic generation signal. This symmetry breaking, together with strong electron-phonon coupling, promotes the formation of self-trapped excitons. The wavelength-dependent linear dichroism reversal phenomenon reflects a k-space rotation of the dominant transition dipole moment orientation, a general feature of low-symmetry semiconductors that is further enhanced here by the ferroelectric structural distortion. The BiSeBr nanowire photodetector translates these physical mechanisms into device functionality. It exhibits broadband photoresponse from ultraviolet to near-infrared (350 to 1060 nm), with a responsivity of 2.4 × 104 A W-1, a specific detectivity of 3.3 × 1013 Jones, and a fast response time of 389 μs. The detector resolves a clear polarization sensitivity reversal between the visible and near-infrared regions. These results establish BiSeBr as a platform for broadband polarization-sensitive photodetection in which multifunctionality is not achieved by stacking disparate materials, but emerges from the intrinsic synergy between ferroelectricity and strong electron-phonon coupling within a single quasi-one-dimensional vdW crystal.

This study presents what we believe to be a novel chalcogenide glass composition, Ga0.8As34.2Sb5S60, as a gain medium for mid-infrared fiber lasers. A systematic investigation was conducted on the thermal stability, absorption, and mid-infrared emission properties of rare-earth (Tm3+, Ho3+, Dy3+, Pr3+) -doped glasses. Few-mode double-clad fibers were fabricated, exhibiting a high rare-earth solubility up to 2000 ppmw and record-low optical losses (0.31 dB/m for Ho3+ -doped fiber and 0.57 dB/m for Pr3+ -doped fiber). Dy3+ - and Tm3+ -doped fibers also achieved low losses of approximately 1-2 dB/m at present. Combined with the high rare-earth solubility and excellent thermal stability, these fibers demonstrate significant potential for high-performance fiber lasers operating in the 2-5 µm wavelength range.

We perform a systematical investigation on the influence of oxygen content in Sr2-xLaxIrO4-δcompounds by comparing the physical properties of the as-prepared Sr2-xLaxIrO4-δsamples, the Sr2-xLaxIrO4-δsamples after annealing under high oxygen pressure and the samples synthesized directly under high oxygen pressure. It is found that there are a lot of oxygen vacancies in the as-prepared Sr2-xLaxIrO4-δsamples, which is rarely reported before. The annealing treatment to the Sr2-xLaxIrO4-δsamples and the synthesis of Sr2-xLaxIrO4-δsamples under oxygen pressure could substantially increase the oxygen content of the samples. The charge carrier densities are much higher in the Sr2-xLaxIrO4-δsamples after annealing treatment and in the samples synthesized under oxygen pressure comparing to those in the as-prepared samples. With the increase of oxygen content, the electrical conductivity of the Sr2-xLaxIrO4-δsamples is substantially enhanced. The present work suggests that the annealing treatment and the synthesis of doped Sr2IrO4-δsamples under high oxygen pressure could be meaningful approaches in further exploration of new physical phenomena and possible superconductivity in doped Sr2IrO4-δcompounds.

Single-phase PdTe nanoflakes are prepared by using a facile cation exchange reaction strategy, which naturally avoids the interference of impurity phases such as PdTe2. The distinct anisotropy in the temperature dependence of upper critical fields and the presence of Berezinskii-Kosterlitz-Thouless transition provide dual evidence of intrinsic 2D superconductivity in PdTe nanoflakes. The fabrication of PdTe nanoflakes with simple crystal structure provides an excellent material platform for capturing the long-sought yet elusive Majorana fermions and developing topological quantum devices.

A series of La3-xTbxNi2O7-δ samples have been synthesized for the first time, and the effects of Tb doping in La3Ni2O7-δ are investigated through a comprehensive investigation on the structural parameters, electrical transport, and magnetic properties of the La3-xTbxNi2O7-δ samples. Novel magnetic ordered state has been observed both in the as-prepared La3-xTbxNi2O7-δ compounds and in the samples after high oxygen pressure annealing. The high oxygen pressure annealing results in substantial enhancement of the oxygen content and the increase of nominal valence state of Ni in the La3-xTbxNi2O7-δ samples, leading to an enhanced conductivity. The present work could contribute to the exploration of possible ambient pressure superconductivity in doped La3Ni2O7-δ systems.

While extensive research has been dedicated to plasmon tuning within non-noble metals, prior investigations primarily concentrated on markedly augmenting the inherently low concentration of free carriers in materials with minimal consideration given to the influence of electron orbitals on surface plasmons. Here, we achieve successful intercalation of Au atoms into the layered structure of Fe3GeTe2 (FGT), thereby exerting control over the orbital electronic states or structure of FGT. This intervention not only amplifies the charge density and electron mobility but also mitigates the loss associated with interband transitions, resulting in increased two-dimensional FGT surface plasmon activity. As a consequence, Au-intercalated FGT detects crystal violet molecules as a surface-enhanced Raman scattering substrate, and the detection lines are 3 orders of magnitude higher than before Au intercalation. Our work provides insight for further studies on plasmon effects and the relation between surface plasmon resonance behavior and electronic structures.

Perpendicular optical reversal of the linear dichroism transition has promising applications in polarization-sensitive optoelectronic devices. We perform a systematical study on the in-plane optical anisotropy of quasi-one-dimensional PdBr 2 by using combined measurements of the angle-resolved polarized Raman spectroscopy（ARPRS） and anisotropic optical absorption spectrum. The analyses of ARPRS data validate the anisotropic Raman properties of the PdBr 2 flake.And anisotropic optical absorption spectrum of PdBr 2 nanoflake demonstrates distinct optical linear dichroism reversal. Photodetector constructed by PdBr 2 nanowire exhibits high responsivity of 747 A·W -1 and specific detectivity of 5.8×10 12 Jones. And the photodetector demonstrates prominent polarization-sensitive photoresponsivity under 405-nm light irradiation with large photocurrent anisotropy ratio of 1.56, which is superior to those of most of previously reported quasi-one-dimensional counterparts. Our study offers fundamental insights into the strong optical anisotropy exhibited by PdBr 2 , establishing it as a promising candidate for miniaturization and integration trends of polarization-related applications.

An anisotropic flat band fermion system with a novel dispersion that is linear along one direction and cubic along another is proposed in Phys. Rev. X. 13, 021012 (2023). We study the effects of Coulomb interaction in this fermion system by renormalization group theory and Dyson-Schwinger gap equation. We perform renormalizaton group analysis and find that fermion velocity is always restored along the direction that the fermions take cubic dispersion originally. Accordingly, the system takes the similar behaviors to the two-dimensional Dirac fermion system with Coulomb interaction in the low energy regime. Based on Dyson-Schwinger gap equation method, we find that an excitonic gap is generated if the Coulomb strength is large enough, and the system becomes a novel excitonic Chern insulator with quantized anomalous Hall conductivity. Observable quantities of this system in free case, under weak and strong enough Coulomb interaction are all analyzed.

The structural, electrical and magnetic properties of a series of La3-xSrxNi2O7-δ polycrystalline samples have been systematically investigated with and without high-pressure oxygen annealing. Without annealing, the introduction of Sr at La site leads to a moderate enhancement of conductivity. The high-pressure oxygen annealing leads to an increase of oxygen content by ∼1.08%. Consequently, the conductivity of the annealing samples is significantly enhanced comparing to the untreated samples. The La3-xSrxNi2O7-δ samples exhibit metal-like behavior in the whole temperature range with annealing, which is due to the hole doping effect. The present results could contribute to the exploration of possible ambient superconductivity in La3Ni2O7-δ system.

The recent discovery of superconductivity in the bilayer nickelate La3Ni2O7 under high pressure has garnered significant interest due to its high transition temperature surpassing the liquid nitrogen limit. This breakthrough has prompted an extensive amount of research aimed at identifying new superconducting nickelates and elucidating the underlying mechanism responsible for superconductivity in La3Ni2O7. Here we report our findings on the effect of Nd doping in La3Ni2O7. Electrical transport measurements conducted at ambient pressure reveal that as the Nd doping concentration increases, La3-xNdxNi2O7 (with x = 0, 0.3, 0.6, 0.9) samples transition from a bad metal to a semiconductor. However, the density wave transition temperature remains unaffected across all La3-xNdxNi2O7 samples. Magnetic property investigations indicate that all doped samples exhibit paramagnetic behavior. Furthermore, we performed resistance measurements under high pressure on the undoped and doped samples. All the samples show a signature of superconductivity at about 80 K under pressure. Our observations extend the scope of doping studies in La3Ni2O7, which will aid in the exploration of the superconducting mechanism within this promising nickelate compound.

The lattice parameters, valence states of Ir ions, and electrical and magnetic properties of a series of Sr2-xLaxIrO4 polycrystalline samples have been systematically investigated with and without high temperature vacuum annealing. The annealing process leads to loss of oxygen content by 1.86

Chalcogenide glasses with less optical losses are highly demanded as optical materials for micro lense, waveguide and fiber devices. However, it is still challengeable to reduce the optical losses in infrared chalcogenide glasses with opaque visible light. Herein, an improved 3D distribution of scattering sources is established in this study to test and compare the concentration and distribution of defects in As38S62, Ge28Sb12Se60 and As40Se60 chalcogenide glasses. Furthermore, by comparing the scattering images of serial As40Se60 glass prepared under various melting, quenching and annealing temperatures, the preparation process was optimized to reduce its scattering loss. In addition, this study introduced a scheme that could be widely applied to optimize processing of other infrared glasses and devices glass to reduce their scattering losses.

Superconductivity was discovered in (InSe2)xNbSe2. The materials are crystallized in a unique layered structure where bonded InSe2 layers are intercalated into the van der Waals gaps of 2H-phase NbSe2. The (InSe2)0.12NbSe2 superconductor exhibits a superconducting transition at 11.6 K and critical current density of 8.2 × 105 A/cm2. Both values are the highest among all transition metal dichalcogenide superconductors at ambient pressure. The present finding provides an ideal material platform for further investigation of superconducting-related phenomena in transition metal dichalcogenides.

As a rediscovered ternary two-dimensional (2D) material, defect-rich Znln2S4 has great potential for energy-harvesting applications. However, the effect of defects on its physical properties and device performance remains elusive. Herein, we explored the influence of defects (S vacancies and In–Zn substitutions) in few-layer Znln2S4 on the charge transport and photoelectric performance. It is demonstrated that the defect-rich Znln2S4 device exhibits two-dimensional variable range hopping transport mechanism, with uniform charge transport along the channel and low contact resistance at the electrical contacts of Znln2S4/Au. Importantly, due to the contribution of the donor and acceptor energy levels inside the bandgap, the flake exhibits pronounced extrinsic absorption, leading to the competitive photodetector performance under sub-bandgap photo-excitation. Explicitly, the device exhibits a maximum responsivity of 4.08 × 104 A W−1, a photo-gain of >108 electrons per photon, and a specific detectivity of ∼1015 Jones under 532 nm laser excitation, with detection wavelength extending from 400 to 980 nm. Our findings underscore the significant potential of defect-engineering to enrich the functionalities of 2D semiconductors.

Nonlinear optics plays important roles in the research of fundamental physics and the applications of high-performance optoelectronic devices. The bulk nonlinear optical responses arise from the uniform light absorption in noncentrosymmetric crystals, and hence are usually considered to be the collective phenomena of all atoms. Here we show, in contrast to this common expectation, the nonlinear optical responses in antiferromagnets can be selectively accumulated near the surfaces, representing a skin effect. This is because the inversion symmetry, despite being broken globally by magnetism, is barely violated locally deeply inside these antiferromagnets. Using A-type layered antiferromagnets as the representatives, we predict that the spatial-dependent nonlinear optical responses, such as the bulk photovoltaic effect and second harmonic generation, are notable in the top- and bottommost layers and decay rapidly when moving away from the surfaces. Such a phenomenon is strongly associated with the antiferromagnetism and exists in a broad range of antiferromagnets composed of centrosymmetric sublattices, offering promising device applications using these antiferromagnets. Our work uncovers a previously overlooked property of nonlinear optical responses and opens new opportunities for high-performance antiferromagnetic optospintronics.

Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr 2 IrO 4 . It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr 2-x Pb x IrO 4 . The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr 2 IrO 4 matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr 2 IrO 4 systems.

It is difficult to perfectly analyze the enhancement mechanism of two-dimensional (2D) materials and their combination with precious metals as surface enhanced Raman scattering (SERS) substrates using chemical enhancement mechanisms. Here, we propose a new mentality based on the coupling effect of neighboring electron orbitals to elucidate the electromagnetic field enhancement mechanism of single-atom-layer Au clusters embedded in double-layer 2H-TaS2 for SRES sensing. The insertion of Au atoms into the 2H-TaS2 interlayer was verified by XRD, AFM, and HRTEM, and a SERS signal enhancement of 2 orders of magnitude was obtained compared to the pure 2H-TaS2. XPS and micro-UV/vis-NIR spectra indicate that the outer electrons of neighboring Au and 2H-TaS2 overlap and migrate from Au to 2H-TaS2. First-principles calculations suggest strong electronic coupling between Au and 2H-TaS2. This study offers insights into SERS enhancement in nonprecious metal compounds and guides the development of new SERS substrates.