Due to their unique characteristics, two-dimensional (2D) materials have drawn great attention as promising candidates for the next generation of integrated circuits, which generate a calculation unit with a new working mechanism, called a logic transistor. To figure out the application prospects of logic transistors, exploring the temperature dependence of logic characteristics is important. In this work, we explore the temperature effect on the electrical characteristic of a logic transistor, finding that changes in temperature cause transformation in the calculation: logical output converts from ‘AND’ at 10 K to ‘OR’ at 250 K. The transformation phenomenon of temperature regulation in logical output is caused by energy band which decreases with increasing temperature. In the experiment, the indirect band gap of MoS₂ shows an obvious decrease from 1.581 eV to 1.535 eV as the temperature increases from 10 K to 250 K. The change of threshold voltage with temperature is consistent with the energy band, which confirms the theoretical analysis. Therefore, as a promising material for future integrated circuits, the demonstrated characteristic of 2D transistors suggests possible application for future functional devices.

Being parent materials of two-dimensional (2D) crystals, van der Waals layered materials have received revived interest. In most 2D materials, the interaction between electrons is negligible. Introducing the interaction can give rise to a variety of exotic properties. Here, via intercalating a van der Waals layered compound VS₂, we find evidence for electron correlation by extensive magnetic, thermal, electrical, and thermoelectric characterizations. The low temperature Sommerfeld coefficient is 64 mJ·K^-2·mol^-1 and the Kadowaki-Woods ratio r_KW～0.20a₀. Both supports an enhancement of the electron correlation. The temperature dependences of the resistivity and thermopower indicate an important role played by the Kondo effect. The Kondo temperature T_K is estimated to be around 8 K. Our results suggest intercalation as a potential means to engineer the electron correlation in van der Waals materials, as well as 2D materials.

Two-dimensional (2D) materials received large amount of studies because of the enormous potential in basic science and industrial applications. Monolayer Pd₂Se₃ is a fascinating 2D material that was predicted to possess excellent thermoelectric, electronic, transport, and optical properties. However, the fabrication of large-scale and high-quality monolayer Pd₂Se₃ is still challenging. Here, we report the synthesis of large-scale and high-quality monolayer Pd₂Se₃ on graphene-SiC (0001) by a two-step epitaxial growth. The atomic structure of Pd₂Se₃ was investigated by scanning tunneling microscope (STM) and confirmed by non-contact atomic force microscope (nc-AFM). Two subgroups of Se atoms have been identified by nc-AFM image in agreement with the theoretically predicted atomic structure. Scanning tunneling spectroscopy (STS) reveals a bandgap of 1.2 eV, suggesting that monolayer Pd₂Se₃ can be a candidate for photoelectronic applications. The atomic structure and defect levels of a single Se vacancy were also investigated. The spatial distribution of STS near the Se vacancy reveals a highly anisotropic electronic behavior. The two-step epitaxial synthesis and characterization of Pd₂Se₃ provide a promising platform for future investigations and applications.

Despite the apparent ubiquity and variety of quantum spin liquids in theory, experimental confirmation of spin liquids remains to be a huge challenge. Motivated by the recent surge of evidences for spin liquids in a series of candidate materials, we highlight the experimental schemes, involving the thermal Hall transport and spectrum measurements, that can result in smoking-gun signatures of spin liquids beyond the usual ones. For clarity, we investigate the square lattice spin liquids and theoretically predict the possible phenomena that may emerge in the corresponding spin liquids candidates. The mechanisms for these signatures can be traced back to either the intrinsic characters of spin liquids or the external field-driven behaviors. Our conclusion does not depend on the geometry of lattices and can broadly apply to other relevant spin liquids.

A feasible neuron model can be effective to estimate the mode transition in neural activities in a complex electromagnetic environment. When neurons are exposed to electromagnetic field, the continuous magnetization and polarization can generate nonlinear effect on the exchange and propagation of ions in the cell, and then the firing patterns can be regulated completely. The conductivity of ion channels can be affected by the temperature and the channel current is adjusted for regulating the excitability of neurons. In this paper, a phototube and a thermistor are used to the functions of neural circuit. The phototube is used to capture external illumination for energy injection, and a continuous signal source is obtained. The thermistor is used to percept the changes of temperature, and the channel current is changed to adjust the excitability of neuron. This functional neural circuit can encode the external heat (temperature) and illumination excitation, and the dynamics of neural activities is investigated in detail. The photocurrent generated in the phototube can be used as a signal source for the neural circuit, and the thermistor is used to estimate the conduction dependence on the temperature for neurons under heat effect. Bifurcation analysis and Hamilton energy are calculated to explore the mode selection. It is found that complete dynamical properties of biological neurons can be reproduced in spiking, bursting, and chaotic firing when the phototube is activated as voltage source. The functional neural circuit mainly presents spiking states when the photocurrent is handled as a stable current source. Gaussian white noise is imposed to detect the occurrence of coherence resonance. This neural circuit can provide possible guidance for investigating dynamics of neural networks and potential application in designing sensitive sensors.

The nonradiative charge-transfer processes of Be³⁺(1s)/B⁴⁺(1s) colliding with He(1s²) are investigated by the quantum-mechanical molecular orbital close-coupling (QMOCC) method from 10 eV/u to 1800 eV/u. Total and state-selective cross sections are obtained and compared with other results available. Although the incident ions have the same number of electrons and collide with the same target, their cross sections are different due to the differences in molecular structure. For Be³⁺(1s) + He(1s²), only single-electron-capture (SEC) states are important and the total cross sections have a broad maximum around E=150 eV/u. While for B⁴⁺(1s) + He(1s²), both the SEC and double-electron-capture (DEC) processes are important, and the total SEC and DEC cross sections decrease rapidly with the energy decreasing.

The dissolution of transition metal (TM) cations from oxide cathodes and the subsequent migration and deposition on the anode lead to the deconstruction of cathode materials and uncontrollable growth of solid electrode interphase (SEI). The above issues have been considered as main causes for the performance degradation of lithium-ion batteries (LIBs). In this work, we reported that the solid oxide electrolyte Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) coating on polyethylene (PE) polymer separator can largely block the TM dissolution and deposition in LIBs. Scanning electron microscopy (SEM), second ion mass spectroscopy (SIMS), and Raman spectroscopy characterizations reveal that the granular surface of the LATP coating layer is converted to a dense morphology due to the reduction of LATP at discharge process. The as-formed dense surface layer can effectively hinder the TM deposition on the anode electrode and inhibit the TM dissolution from the cathode electrode. As a result, both the LiCoO₂/SiO-graphite and LiMn₂O₄/SiO-graphite cells using LATP coated PE separator show substantially enhanced cycle performances compared with those cells with Al₂O₃ coated PE separator.

Quantum theory of surface plasmons is very important for studying the interactions between light and different metal nanostructures in nanoplasmonics. In this work, using the canonical quantization method, the SPPs on nanowires and their orbital and spin angular momentums are investigated. The results show that the SPPs on nanowire carry both orbital and spin momentums during propagation. Later, the result is applied to the plasmonic nanowire waveguide to show the agreement of the theory. The study is helpful for the nano wire based plasmonic interactions and the quantum information based optical circuit in the future.

High quality 0.02 mol%, 0.05 mol%, and 0.08 mol% Fe:β-Ga₂O₃ single crystals were grown by the floating zone method. The crystal structure, optical, electrical, and thermal properties were measured and discussed. Fe:β-Ga₂O₃ single crystals showed transmittance of higher than 80% in the near infrared region. With the increase of the Fe doping concentration, the optical bandgaps reduced and room temperature resistivity increased. The resistivity of 0.08 mol% Fe:β-Ga₂O₃ crystal reached to 3.63×10¹¹ Ω·cm. The high resistivity Fe:β-Ga₂O₃ single crystals could be applied as the substrate for the high-power field effect transistors (FETs).

Electron energy relaxation time τ is one of the key physical parameters for electronic materials. In this study, we develop a new technique to measure τ in a semiconductor via monochrome picosecond (ps) terahertz (THz) pump and probe experiment. The special THz pulse structure of Chinese THz free-electron laser (CTFEL) is utilized to realize such a technique, which can be applied to the investigation into THz dynamics of electronic and optoelectronic materials and devices. We measure the THz dynamical electronic properties of high-mobility n-GaSb wafer at 1.2 THz, 1.6 THz, and 2.4 THz at room temperature and in free space. The obtained electron energy relaxation time for n-GaSb is in line with that measured via, e.g., four-wave mixing techniques. The major advantages of monochrome ps THz pump-probe in the study of electronic and optoelectronic materials are discussed in comparison with other ultrafast optoelectronic techniques. This work is relevant to the application of pulsed THz free-electron lasers and also to the development of advanced ultrafast measurement technique for the investigation of dynamical properties of electronic and optoelectronic materials.

We report a p24 (HIV disease biomarker) detection assay using an MgO-based magnetic tunnel junction (MTJ) sensor and 20-nm magnetic nanoparticles. The MTJ array sensor with sensing area of 890×890 μ² possessing a sensitivity of 1.39%/Oe was used to detect p24 antigens. It is demonstrated that the p24 antigens could be detected at a concentration of 0.01 μg/ml. The development of bio-detection systems based on magnetic tunnel junction sensors with high-sensitivity will greatly benefit the early diagnosis of HIV.

Point and line defects are of vital importance to the physical and chemical properties of certain two-dimensional (2D) materials. Although electron beams have been demonstrated to be capable of creating single-and multi-atom defects in 2D materials, the products are often random and difficult to predict without theoretical inputs. In this study, the thermal motion of atoms and electron incident angle were additionally considered to study the vacancy evolution in a black phosphorus (BP) monolayer by using an improved first-principles molecular dynamics method. The P atoms in monolayer BP tend to be struck away one by one under an electron beam within the displacement threshold energy range of 8.55-8.79 eV, which ultimately induces the formation of a zigzag-like chain vacancy. The chain vacancy is a thermodynamically metastable state and is difficult to obtain by conventional synthesis methods because the vacancy formation energy of 0.79 eV/edge atom is higher than the typical energy in monolayer BP. Covalent-like quasi-bonds and a charge density wave are formed along the chain vacancy, exhibiting rich electronic properties. This work proposes a theoretical protocol for simulating a complete elastic collision process of electron beams with 2D layers and will facilitate the establishment of detailed theoretical guidelines for experiments on 2D material etching using focused high-energy electron beams.