Direct Observation of Nanoscale Light Confinement without Metal.

Manipulation of light below the diffraction limit forms the basis of nanophotonics. Metals can confine light at the subwavelength scale but suffer from high loss of energy. Recent reports have theoretically demonstrated the possibility of light confinement below the diffraction limit using transparent dielectric metamaterials.

Photophysical Pathways in Highly Sensitive Cs AgBiBr Double-Perovskite Single-Crystal X-Ray Detectors.

The sensitive detection of X-rays embodies an important research area, being motivated by a common desire to minimize the radiation doses required for detection. Among metal halide perovskites, the double-perovskite Cs AgBiBr system has emerged as a promising candidate for the detection of X-rays, capable of high X-ray stability and sensitivity (105 μC Gy cm ). Herein, the important photophysical pathways in single-crystal Cs AgBiBr are detailed at both room (RT) and liquid-nitrogen (LN T) temperatures, with emphasis made toward understanding the carrier dynamics that influence X-ray sensitivity.

Giant Electron-Phonon Coupling and Deep Conduction Band Resonance in Metal Halide Double Perovskite.

The room-temperature charge carrier mobility and excitation-emission properties of metal halide perovskites are governed by their electronic band structures and intrinsic lattice phonon scattering mechanisms. Establishing how charge carriers interact within this scenario will have far-reaching consequences for developing high-efficiency materials for optoelectronic applications. Herein we evaluate the charge carrier scattering properties and conduction band environment of the double perovskite CsAgBiBr via a combinatorial approach; single crystal X-ray diffraction, optical excitation and temperature-dependent emission spectroscopy, resonant and nonresonant Raman scattering, further supported by first-principles calculations.

Tunable and switchable magnetic dipole patterns in nanostructured superconductors.

Design and manipulation of magnetic moment arrays have been at the focus of studying the interesting cooperative physical phenomena in various magnetic systems. However, long-range ordered magnetic moments are rather difficult to achieve due to the excited states arising from the relatively weak exchange interactions between the localized moments. Here, using a nanostructured superconductor, we investigate a perfectly ordered magnetic dipole pattern with the magnetic poles having the same distribution as the magnetic charges in an artificial spin ice.

Nematic superconducting state in iron pnictide superconductors.

Nematic order often breaks the tetragonal symmetry of iron-based superconductors. It arises from regular structural transition or electronic instability in the normal phase. Here, we report the observation of a nematic superconducting state, by measuring the angular dependence of the in-plane and out-of-plane magnetoresistivity of BaKFeAs single crystals.

Near-Field Mapping of Optical Fabry-Perot Modes in All-Dielectric Nanoantennas.

Subwavelength optical resonators and scatterers are dramatically expanding the toolset of the optical sciences and photonics engineering. By offering the opportunity to control and shape light waves in nanoscale volumes, recent developments using high-refractive-index dielectric scatterers gave rise to efficient flat-optical components such as lenses, polarizers, phase plates, color routers, and nonlinear elements with a subwavelength thickness. In this work, we take a deeper look into the unique interaction of light with rod-shaped amorphous silicon scatterers by tapping into their resonant modes with a localized subwavelength light source-an aperture scanning near-field probe.

Electrically Driven Unidirectional Optical Nanoantennas.

Directional antennas revolutionized modern day telecommunication by enabling precise beaming of radio and microwave signals with minimal loss of energy. Similarly, directional optical nanoantennas are expected to pave the way toward on-chip wireless communication and information processing. Currently, on-chip integration of such antennas is hampered by their multielement design or the requirement of complicated excitation schemes.

Controlled Generation of Quantized Vortex-Antivortex Pairs in a Superconducting Condensate.

Quantized vortices, as topological defects, play an important role in both physics and technological applications of superconductors. Normally, the nucleation of vortices requires the presence of a high magnetic field or current density, which allow the vortices to enter from the sample boundaries. At the same time, the controllable generation of individual vortices inside a superconductor is still challenging.

Healing Effect of Controlled Anti-Electromigration on Conventional and High-T Superconducting Nanowires.

The electromigration process has the potential capability to move atoms one by one when properly controlled. It is therefore an appealing tool to tune the cross section of monoatomic compounds with ultimate resolution or, in the case of polyatomic compounds, to change the stoichiometry with the same atomic precision. As demonstrated here, a combination of electromigration and anti-electromigration can be used to reversibly displace atoms with a high degree of control.

Statistics of localized phase slips in tunable width planar point contacts.

The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads.

Upconversion fluorescent and X-ray-sensitive bifunctional nanoprobes for assessing the penetrability of inorganic nanoparticles in the digestive system.

Nanotechnology is receiving increasing attention due to its fantastic advantages and potential applications in nanofood and nanomedicine. However, the safety of touching manufactured nanoparticles is still uncertain for human beings. Here, we track inorganic nanoparticles in the digestive system of the mouse through upconversion fluorescence and X-ray imaging, and try to demonstrate whether or not the inorganic nanoparticles will penetrate the digestive system to enter the blood system.

Nanoscale assembly of superconducting vortices with scanning tunnelling microscope tip.

Vortices play a crucial role in determining the properties of superconductors as well as their applications. Therefore, characterization and manipulation of vortices, especially at the single-vortex level, is of great importance. Among many techniques to study single vortices, scanning tunnelling microscopy (STM) stands out as a powerful tool, due to its ability to detect the local electronic states and high spatial resolution.

Determination of the spin-lifetime anisotropy in graphene using oblique spin precession.

We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane.

Thermal and quantum depletion of superconductivity in narrow junctions created by controlled electromigration.

Superconducting nanowires currently attract great interest due to their application in single-photon detectors and quantum-computing circuits. In this context, it is of fundamental importance to understand the detrimental fluctuations of the superconducting order parameter as the wire width shrinks. In this paper, we use controlled electromigration to narrow down aluminium nanoconstrictions.

Tuning the Magnetic Interactions and Relaxation Dynamics of Dy2 Single-Molecule Magnets.

Efficient modulation of single-molecule magnet (SMM) behavior was realized by deliberate structural modification of the Dy2 cores of [Dy2(a'povh)2(OAc)2(DMF)2] (1) and [Zn2Dy2(a'povh)2(OAc)6]⋅4 H2O (2; H2a'povh = N'-[amino(pyrimidin-2-yl)methylene]-o-vanilloyl hydrazine). Compound 1 having fourfold linkage between the two dysprosium ions shows high-performance SMM behavior with a thermal energy barrier of 322.1 K, whereas only slow relaxation is observed for compound 2 with only twofold connection between the dysprosium ions.

Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors.

Lateral magnetic near-field imaging of plasmonic nanoantennas with increasing complexity.

The design of many promising, newly emerging classes of photonic metamaterials and subwavelength confinement structures requires detailed knowledge and understanding of the electromagnetic near-field interactions between their building blocks. While the electric field distributions and, respectively, the electric interactions of different nanostructures can be routinely measured, for example, by scattering near-field microscopy, only recently experimental methods for imaging the magnetic field distributions became available. In this paper, we provide direct experimental maps of the lateral magnetic near-field distributions of variously shaped plasmonic nanoantennas by using hollow-pyramid aperture scanning near-field optical microscopy (SNOM).

Dynamic visualization of nanoscale vortex orbits.

Due to the atomic-scale resolution, scanning tunneling microscopy is an ideal technique to observe the smallest objects. Nevertheless, it suffers from very long capturing times in order to investigate dynamic processes at the nanoscale. We address this issue, for vortex matter in NbSe2, by driving the vortices using an ac magnetic field and probing the induced periodic tunnel current modulations.

Theory of the kinetics of luminescence and its temperature dependence for Ag nanoclusters dispersed in a glass host.

We have measured and fitted the kinetics of luminescence of Ag nanoclusters homogeneously dispersed within the bulk of an oxyfluoride glass, with various sample temperatures. The balance equations for the populations of the excited singlet and triplet states of the Ag nanoclusters are proposed and used in this fitting while taking into account inter-system crossing between the singlet and triplet states and their wavelength dependent spontaneous decay to the ground singlet state. The involved energy barriers and rate constants and spontaneous emission cross-sections for the excited singlet and triplet states are evaluated.

Mapping magnetic near-field distributions of plasmonic nanoantennas.

We present direct experimental mapping of the lateral magnetic near-field distribution in plasmonic nanoantennas using aperture scanning near-field optical microscopy (SNOM). By means of full-field simulations it is demonstrated how the coupling of the hollow-pyramid aperture probe to the nanoantenna induces an effective magnetic dipole which efficiently excites surface plasmon resonances only at lateral magnetic field maxima. This excitation in turn affects the detected light intensity enabling the visualization of the lateral magnetic near-field distribution of multiple odd and even order plasmon modes with subwavelength spatial resolution.

Method for the solution of the nucleation problem in arbitrary mesoscopic superconductors: theory and application.

We present a method for finding the condensate distribution at the nucleation of superconductivity for arbitrary polygons. The method is based on conformal mapping of the analytical solution of the linearized Ginzburg-Landau problem for the disk and uses the superconducting gauge for the magnetic potential proposed earlier. As a demonstration of the method's accuracy, we calculate the distribution of the order parameter in regular polygons and compare the obtained solutions with available numerical results.

Origin of visible photoluminescence from arrays of vertically arranged Si-nanopillars decorated with Si-nanocrystals.

Arrays of vertically aligned Si-nanopillars, with average diameters of 100 nm and 5 μm length, have been prepared by wet chemical etching of crystalline silicon in a special manner. Samples with smooth- and porous-walled nanopillars have been studied. In the case of the latter, Si-nanocrystals, passivated with SiO(x), decorating the surface of the nanopillars are identified by the means of TEM and FTIR.

Polarization memory of white luminescence of Ag nanoclusters dispersed in glass host.

A mechanism for white luminescence of Ag nanoclusters dispersed in oxyfluoride glass host has been revealed by studying a temperature dependence of its polarization memory. The spectral dependence of the polarization memory indicates the presence of a variety of Ag nanoclusters, particularly emitting in the blue, green and red. Temperature activated intercluster energy transfer has been found responsible for white luminescence.

Energy level diagram and kinetics of luminescence of Ag nanoclusters dispersed in a glass host.

A site-selective spectroscopy study of Ag nanoclusters dispersed in oxyfluoride glass hosts has been carried out. The nano- to millisecond, essentially non-exponential, luminescence kinetics of Ag nanoclusters has been detected in the spectral range from 450 to 1000 nm, when excited at discrete wavelengths in the range 250 to 450 nm. Based on these experimental observations, the energy level configuration coordinate diagram for the involved ground and excited singlet/triplet states of the Ag nanoclusters has been proposed and confirmed by the density functional theory (DFT).

The harmonic analysis of cylindrically symmetric proteins: a comparison of Dronpa and a DNA sliding clamp.

The harmonic analysis of two types of proteins with cylindrical symmetry is performed by the Standard Force Field Normal Mode Analysis and by the elastic network model. For both proteins the global elastic modes are assigned to their characteristic topologies. Dronpa is a rigid β-barrel structure, presenting the twisting, bending and breathing motion of a cylindrical rod.