Visible transmission response of nanoscale complementary metamaterials for sensing applications

Metamaterials (MMs) have shown huge potential in sensing applications by detecting their optical properties, which can be designed to operate at frequencies from visible to mid-IR. Here we constructed complementary split ring resonator (CSRR) based metamaterials in nanoscale with unit length of 100 nm and slit width of 30 nm, and observed obvious responses in the visible waveband from 600 to 900 nm. These visible responses show a good tunability with the structure's geometry, and are well suited for dielectric detection. We demonstrated good refractive index sensing of CSRR based metamaterials in the visible region under both 0° and 90° polarized incidence. Our results extend the study of CSRR based metamaterials to the visible region, which is expected to deepen the understanding of the response mechanism of CSRRs and benefit their sensing applications in the visible region.     

Core-shell metallic alloy nanopillars-in-dielectric hybrid metamaterials with magneto-plasmonic coupling

Combining plasmonic and magnetic properties, namely magneto-plasmonic coupling, inspires great research interest and the search for magneto-plasmonic nanostructure becomes considerably critical. Here we designed a nanopillar-in-matrix structure with core–shell alloyed nanopillars for both BaTiO₃ (BTO)-Au_0.5Co_0.5 (AuCo) and BTO-Au_0.25Cu_0.25Co_0.25Ni_0.25 (AuCuCoNi) hybrid systems, i.e., ferromagnetic alloy cores (e.g., Co or CoNi) with plasmonic shells (e.g., Au or Au/Cu). These core–shell alloy nanopillars are uniformly embedded into a dielectric BTO matrix to form a vertically aligned nanocomposite (VAN) structure. Both hybrid systems present excellent epitaxial quality and interesting multi-functionality, e.g., high magnetic anisotropy, magneto-optical coupling response, tailorable plasmonic resonance wavelength, tunable hyperbolic properties and strong optical anisotropy. These alloyed nanopillars-in-matrix designs provide enormous potential for complex hybrid material designs with multi-functionality and demonstrate strong interface enabled magneto-plasmonic coupling along with plasmonic and magnetic performance.     

Strong electronic coupling and ultrafast electron transfer between PbS quantum dots and TiO2 nanocrystalline films

Hot carrier and multiple exciton extractions from lead salt quantum dots (QDs) to TiO(2) single crystals have been reported. Implementing these ideas on practical solar cells likely requires the use of nanocrystalline TiO(2) thin films to enhance the light harvesting efficiency. Here, we report 6.4 ± 0.4 fs electron transfer time from PbS QDs to TiO(2) nanocrystalline thin films, suggesting the possibility of extracting hot carriers and multiple excitons in solar cells based on these materials.     

Strong coupling theory of the charge-density-wave state

Electron-phonon coupling is considered in the strong coupling approximation in order to explain the formation of the charge-density-wave state. The theory gives the expression for the critical temperature as a function of the effective electron-phonon coupling, and the isotopic effect in the critical temperature can be evaluated.     

Strong electron-ion coupling in gradient halide perovskite heterojunction

The electron-ion coupling in iontronics has great significance and potential for energy conversion and storage devices.However,it is a substantial challenge to integrate iontronics into all-solid-state semiconductor circuits and explore the electron-ion coupling in semiconductor devices.Here,by utilizing the organic-inorganic halide perovskite,we fabricate a planar heterojunction with a gradient distribution of halide anions.The diode-like halide migration was investigated by bias voltage induced asymmetric blue shift in photoluminescence spectrum.This pseudo-ionic diode behaviour was found to result from asymmetric charge injection characterized by I-V curves and gradient-halides-induced vacancy hopping indicated by energy dispersive spectroscopy(EDS).The planar gradient perovskite heterojunction provides a viable route for extending iontronic devices into the regime of all-solid-state semiconductors.     

Relationship between superconductivity and band structures of electrons and phonons

The relationship between superconductivity and band structures of electrons and phonons is established on the basis of a generalized Bardeen-Cooper-Schrieffer model in which the interaction strengths (V ₁₁,V ₁₂,V ₁₂) among and between electron (1) and hole (2) Cooper pairs are differentiated. Elemental superconductors must have local hyperboloidal Fermi surfaces called necks or inverted double caps.     

Universal link between the boson peak and transverse phonons in glass

The physical properties of a topologically disordered amorphous material (glass), such as heat capacity and thermal conductivity, are markedly different from those of its ordered crystalline counterpart. The understanding of these phenomena is a notoriously complex problem. One of the universal features of disordered glasses is the 'boson peak', which is observed in neutron and Raman scattering experiments. The boson peak is typically ascribed to an excess density of vibrational states. Here, we study the nature of the boson peak, using numerical simulations of several glass-forming systems. We discovered evidence suggestive of the equality of the boson peak frequency to the Ioffe-Regel limit for 'transverse' phonons, above which transverse phonons no longer propagate. Our results indicate a possibility that the origin of the boson peak is transverse vibrational modes associated with defective soft structures in the disordered state. Furthermore, we suggest a possible link between slow structural relaxation and fast boson peak dynamics in glass-forming systems.     

负泊松比超材料和结构

负泊松比超材料和结构具有优异的抗剪切性能、抗冲击性能、抗断裂性能、吸能隔振、渗透率可变性能、曲面同向性等力学性能,在航空航天、航海、机械自动化、生物医疗、国防军事、纺织工业等领域具有广泛的应用前景.本文从负泊松比超材料和结构的变形机理出发,综述了内凹结构、旋转刚体结构、手性/反手性结构、纤维/节点结构、折纸结构、褶皱结构、弯曲-诱导结构、螺旋纱线结构等物理模型,这些模型具有广泛的适用性,可运用于轻质夹层板、流体输送、纱线等工程应用,有利于改善结构的使用性能.最后,本文对负泊松比超材料和结构未来的挑战和在航空航天、军事等领域的应用进行了展望,指出利用负泊松比逆转了正泊松比对单轴应力引起的体积和面积变化的补偿效应可有效改善发动机叶片、深空天线以及汽车吸能盒等关键构件的抗冲击性能等,以期为负泊松比超材料和结构的推广应用提供参考.     

有机半导体/金属杂化纳米结构中的强耦合相互作用及超快动力学特性

有源表面等离光子学(active plasmonics)是目前表面等离子体光子学研究的一个重要分支,其基本思想是利用“增益”物质和纳米金属结构相结合形成杂化金属纳米结构,从而克服表面等离子体激元(surface plasmon polariton,SPP)的耗散问题以及实现对SPP光子的外部操作和调制。本文主要针对有机半导体/金属杂化纳米结构,介绍其相关研究结果。结合色散补偿的光谱相干法和超快泵浦-探测瞬态光谱测量技术,分析了J-凝聚/光栅杂化金属纳米结构的静态和瞬态光学特性,揭示了X-SPP的强耦合过程中的相干和非相干相互作用通道,杂化能态的sub/super-radiance现象,以及有机半导体染料中的激子和SPP之间的瞬态相干能量交换过程：“拉比”振荡。实现了10 fs量级的SPP光学特性的外部相干调制。

     

Strong coupling theory and the Josephson current into proximity high-T c junctions

The correlation between the order parameter and the energy gap is studied. Josephson junctions containing proximity systems are described within the framework of the strong coupling theory. The value of the current is affected by the difference between the order parameter at zero frequency and the energy gap. The proximity effect leads to depression of the Josephson current for the high-critical-temperature junctions.     

Electrophysics and electrodynamics of metamaterials

This paper generalizes the main results obtained at the Institute for Theoretical and Applied Electromagnetics of the Scientific Association for High Temperatures of the Russian Academy of Sciences in the design and study of materials with new properties that have no analogs in nature, i.e., the so-called metamaterials. The brief review covers investigations performed since 1987 up to now. It has been demonstrated that new properties of metamaterials are associated with the resonance phenomena, which arise in the propagation of electromagnetic waves in a heterogeneous medium filled with inclusions of special shape. The fundamental aspects of the problem and some of the possible applications have been discussed.     

First-principles study of static nanoscale friction between MoO3 and MoS2

The motion of a nanoscale MoO3 crystal on an MoS2 substrate is an ideal case for the study of the effects of microstructure on macroscopic phenomena like friction, because both components of this system can be prepared with atomically flat surfaces. We apply a recently developed real-space density functional theory method to investigate the energetics of sliding an MoO3 crystal on an MoS2 substrate. We then link the results to simple models based on continuum elastic theory, in order to study the mechanical behavior of the oxide crystals under loads that correspond to realistic situations. Based on these results, we extract estimates of the force which must be applied with an atomic force microscope in order to move the oxide crystal on the substrate, for different orientations of the two components.     

Strong coupling theory and the Josephson current into proximity high-Tc junctions

The correlation between the order parameter and the energy gap is studied. Josephson junctions containing proximity systems are described within the framework of the strong coupling theory. The value of the current is affected by the difference between the order parameter at zero frequency and the energy gap. The proximity effect leads to depression of the Josephson current for the high-critical-temperature junctions.     

Superconducting state in M3C60: Strong vs. weak coupling

The superconducting state in the doped fullerenes is due to strong coupling (e.g.,λ≈2.1 for Rb₃C₆₀) to low-frequency intramolecular modes Ω?Ω _L ≈250 cm^?1 (Ω≡〈Ω²〉^1/2). The analysis is based on an equation describingT _c for any strength of the coupling and on recent isotope effect and NMR data.     

Strong coupling effects on the upper critical field of the heavy-fermion superconductor UBe13

The upper critical fieldH _c2 (T) of a high quality single crystal of UBe₁₃ is studied with very low noise resistivity measurements. It shows a large but finite slope of —45 T/K, an unusual temperature dependence with an inflexion point atT/T _C 0.5 and a large saturated limit forT 0 ofH _c2 (0) = 14 T. The complete temperature dependence ofH _c2 (T) can be described by a simple model of strong coupling superconductor, assuming a full Pauli limitation and the occurence of a non-uniform superconducting state (FFLO state) at low temperature.     

Strong photon-mixing of terahertz waves in semiconductor quantum wells induced by Rashba spin-orbit coupling

We demonstrate that due to the Rashba spin-orbit coupling in semiconductor quantum wells, there is strong photo-mixing by mobile carriers in the terahertz frequency regime. The third order nonlinear current is of the same order of magnitude as the linear order current for an electric field intensity of 10(4)?V?cm(-1) at frequency around 1?THz, a situation easily achievable in a laboratory system. Unlike other nonlinear effects, the nonlinear current density due to the spin-orbit coupling is inversely proportional to the concentration of mobile carriers.