The two-dimensional hexagonal boron nitride (h-BN) has been used as resistive switching (RS) material for memory due to its insulation, good thermal conductivity and excellent thermal/chemical stability. A typical h-BN based RS memory employs a Metal-Insulator-Metal (MIM) vertical structure, in which metal ions pass through the h-BN layers to realize the transition from high resistance state (HRS) to low resistance state (LRS). Alternatively, just like the horizontal structure widely used in the traditional MOS capacitor based memory, the performance of in-plane h-BN memory should also be evaluated to determine its potential applications. As consequence, a horizontal structured resistive memory has been designed in this work by forming freestanding h-BN across Ag nanogap, where the two-dimensional h-BN favored in-plane transport of metal ions to emphasize the RS behavior. As a result, the memory devices showed switching slope down to 0.25 mV/dec, ON/OFF ratio up to 1E8, SET current down to pA and SET voltage down to 180 mV.

In this article, a wideband circularly polarized stacked microstrip patch antenna (CP SMPA) with continuous phase feed characteristics is presented. The designed antenna consists of a square‐loop feeding structure as driven element, four rectangular‐patches and four rotated square‐patches as parasitic elements. First, a square‐loop with arc‐shaped strip is designed to obtain 90° phase difference. Second, four rectangular‐patches are placed next to the square‐loop for generating a CP resonant mode through a capacitive coupling method. Third, four rotated square‐patches are arranged at the top of the rectangular‐patches to excite an additional CP resonant mode. Eventually, the designed CP SMPA features a wide −10‐dB impedance bandwidth (IBW) of 32% (5.93 GHz, 4.98–6.88 GHz), and a broad 3‐dB axial ratio bandwidth of 22.8% (6.15 GHz, 5.45–6.85 GHz).

Localized surface plasmon resonance of cylindrical magneto optical particles provides an important mechanism for the formation of chiral edge states in two-dimensional magneto-optical photonic crystals. These states are an electromagnetic analogy of the so-called chiral edge state's (CESs) in a quantum Hall system where the power transmission is unidirectional due to particular topological properties of the bands. Just like their electronic counterpart, the number of optical CESs in the band gap opened by an applied magnetic field is determined by the sum of the Chern numbers of the lower bands. For a two-dimensional photonic crystal composed of ferrite rods magnetized along their axis, the coupling of the localized surface plasmon resonance states of each rod results in a narrow flat band-gap, which contains one-way edge modes arising from the circulation of the energy flow around each rod excited by the resonance with broken time-reversal symmetry. So far the interpretation of the resonance-related chiral edge states are based on the long-wavelength approximation of the localized surface plasmon resonance of an individual magneto-optical particle. Though the results agree with the experimental results qualitatively, an obvious quantitative deviation is still obvious. In this work we apply the scattering theory to analyze the resonance condition and the features of both the far-field and the near-field at resonance for cylindrical magneto-optical particles. Our calculation shows that the splitting of scattering peaks of different orders will occur due to the magneto-optical effect. Such a split is observed between an (+n)-peak and an (-n) peak, as a sign of the broken time-reversal symmetry, and also between peaks of lower-order and higher-order. Another important feature is the simultaneous occurring of the far-field resonance and the near-field resonance, where the latter is characterized by a peak of energy-flow circulation around the particle. Based on this model the effects of particle size on the resonance peaks are discussed. It is shown that the resonance peaks are moved and broadened with the particle size increasing. The results explain the obvious deviation of the position of the resonance band-gap from the predicted frequency according to the previous long-wavelength approximation. Furthermore, the calculation of a particle of moderately-large size (nearly one-tenth of the incident wavelength) demonstrates the appearance of higher-order modes up to n=4 circling around the particle surface. This implies that these higher-order modes may also make non-trivial contribution to the formation of the flat band-gap observed in a photonic crystal of ferrite-rods and affect the behaviours of the chiral-edge state existing in such a gap. Particularly, it may be helpful in realizing the multimodes of chiral edge states in magneto-optical photonic crystals.

A compact wideband circularly polarized (CP) microstrip slot antenna (MSA) with parasitic elements is designed in this letter. The CP MSA comprises a square-loop sequential-phase (SP) feeding configuration, four rotated rectangular patches, and four L-shaped slots embedded in the ground plane. The square-loop SP feeding structure comprises a square loop and an arc-shaped strip, which could provide a 270° phase difference. Four rotated rectangular patches are placed at the edge of the square-loop feeding configuration using a capacitively tightly coupled feeding method to stimulate the CP resonant mode. After selecting these elements and tuning proper dimensions, the broad operating bandwidths of 4.38–5.25 GHz (18%) for |S11| <–10 dB and 4.65–5.31 GHz (13.2%) for AR <3 dB could be realized. Hence, the designed CP MSA has a potential application value in wireless communication.