Probing higher order optical modes in all-dielectric nanodisk, -square, and -triangle by aperture type scanning near-field optical microscopy

All-dielectric nanoantennas, consisting of high refractive index semiconductor material, are drawing a great deal of attention in nanophotonics. Owing to their ability to manipulate efficiently the flow of light within sub-wavelength volumes, they have become the building blocks of a wide range of new photonic metamaterials and devices. The interaction of the antenna with light is largely governed by its size, geometry, and the symmetry of the multitude of optical cavity modes it supports. Already for simple antenna shapes, unraveling the full modal spectrum using conventional far-field techniques is nearly impossible due to the spatial and spectral overlap of the modes and their symmetry mismatch with incident radiation fields. This limitation can be circumvented by using localized excitation of the antenna. Here, we report on the experimental near-field probing of optical higher order cavity modes (CMs) and whispering gallery modes (WGMs) in amorphous silicon nanoantennas with simple, but fundamental, geometrical shapes of decreasing rotational symmetry: a disk, square, and triangle. Tapping into the near-field using an aperture type scanning near-field optical microscope (SNOM) opens a window on a rich variety of optical patterns resulting from the local excitation of antenna modes of different order with even and odd parity. Numerical analysis of the antenna and SNOM probe interaction shows how the near-field patterns reveal the node positions of – and allows us to distinguish between – cavity and whispering gallery modes. As such, this study contributes to a richer and deeper characterization of the structure of light in confined nanosystems, and their impact on the structuring of the light fields they generate.

Faster and Slower Soliton Phase Shift: Oceanic Waves Affected by Earth Rotation

This research paper investigates the accuracy of a novel computational scheme (Khater II method) by applying this new technique to the fractional nonlinear Ostrovsky (FNO) equation. The accuracy of the obtained solutions was verified by employing the Adomian decomposition (AD) and El Kalla (EK) methods. The AD and EK methods are considered as two of the most accurate semi-analytical schemes. The FNO model is a modified version of the well-known Korteweg–de Vries (KdV) equation that considers the effects of rotational symmetry in space. However, in the KdV model, solutions to the KdV equations substitute this effect with radiating inertia gravity waves, and thus this impact is ignored. The analytical, semi-analytical, and accuracy between solutions are represented in some distinct plots. Additionally, the paper’s novelty and its contributions are demonstrated by comparing the obtained solutions with previously published results.

Tin monosulfide (SnS) epitaxial films grown by RF magnetron sputtering and sulfurization on MgO(100) substrates

The crystallographic and electrical properties of tin monosulfide (SnS) epitaxial thin films grown by RF magnetron sputtering and sulfurization were investigated. The SnS(040)-oriented films were grown on an MgO(100) substrate. Two types of four-fold rotational symmetrical in-plane orientations, offset by 45° from each other, were observed using X-ray diffraction. The rotational symmetry was also observed using cross-sectional transmission electron microscopy. The electrical properties of the SnS films were controlled by varying the sulfurization temperature, and the carrier transport of all the SnS epitaxial films was mainly limited by grain boundary scattering. The activation energies of the carrier concentration before and after sulfurization of the films were estimated to be approximately 0.26 ± 0.02 eV and 0.20 ± 0.01 eV, respectively, based on temperature-dependent Hall measurements. These values mainly correspond to the acceptor level energy of Sn vacancy with a high/low potential barrier height around the grain boundary.

Twofold symmetry of c-axis resistivity in topological kagome superconductor CsV3Sb5 with in-plane rotating magnetic field

In transition metal compounds, due to the interplay of charge, spin, lattice and orbital degrees of freedom, many intertwined orders exist with close energies. One of the commonly observed states is the so-called nematic electron state, which breaks the in-plane rotational symmetry. This nematic state appears in cuprates, iron-based superconductor, etc. Nematicity may coexist, affect, cooperate or compete with other orders. Here we show the anisotropic in-plane electronic state and superconductivity in a recently discovered kagome metal CsV3Sb5 by measuring c-axis resistivity with the in-plane rotation of magnetic field. We observe a twofold symmetry of superconductivity in the superconducting state and a unique in-plane nematic electronic state in normal state when rotating the in-plane magnetic field. Interestingly these two orders are orthogonal to each other in terms of the field direction of the minimum resistivity. Our results shed new light in understanding non-trivial physical properties of CsV3Sb5.

Magnetic field effect on topological properties of Dirac semimetals PdTe2/PtTe2/PtSe2

We investigated magnetic field effect on the topological properties of transition metal dichalcogenide Dirac semimetals (DSMs) PdTe2/PtTe2/PtSe2 based on Wannier-function-based tight-binding (WFTB) model obtained from first-principles calculations. The DSMs PdTe2/PtTe2/PtSe2 undergo a transition from DSMs into Weyl semimetals (WSMs) with four pairs of Weyl points (WPs) in the entire Brillouin zone by splitting Dirac points under external magnetic field B. The positions and energies of WPs vary linearly with the strength of B field under the c-axis magnetic field B. Under the a- and b-axis B field, however, the positions of magnetic-field-inducing WPs deviate slightly from c axis, and their kz coordinates and energies change in a parabolic-like curve with the increasing B field. However, the system opens an axial gap on the A-Γ axis and the gap changes with the direction of B field when the out of c-axis B field is applied. When we further apply the magnetic field in the ac, bc, and ab planes, the results are more diverse compared to the axial magnetic field. Under the ac and bc plane B field, the kz and energies of WPs within angle θ= [0°, 90°] and θ= [90°, 180°] are mirror symmetrically distributed. The distribution of WPs shows broken rotational symmetry under the ab plane B field due to the difference of non-diagonal part of Hamiltonian. Our theoretical findings can provide the useful guideline for the applications of DSM materials under external magnetic field in the future topological electronic devices.

Spontaneous symmetry breaking in persistent currents of spinor polaritons

We predict the spontaneous symmetry breaking in a spinor Bose–Einstein condensate of exciton-polaritons (polaritons) caused by the coupling of its spin and orbital degrees of freedom. We study a polariton condensate trapped in a ring-shaped effective potential with a broken rotational symmetry. We propose a realistic scheme of generating controllable spinor azimuthal persistent currents of polaritons in the trap under the continuous wave optical pump. We propose a new type of half-quantum circulating states in a spinor system characterized by azimuthal currents in both circular polarizations and a vortex in only one of the polarizations. The spontaneous symmetry breaking in the spinor polariton condensate that consists in the switching from co-winding to opposite-winding currents in opposite spin states is revealed. It is characterized by the change of the average orbital angular momentum of the condensate from zero to non-zero values. The radial displacement of the pump spot and the polarization of the pump act as the control parameters. The considered system exhibits a fundamental similarity to a superconducting flux qubit, which makes it highly promising for applications in quantum computing.

Are drivers of northern lights in the ionosphere?

Known as northern lights, auroral spirals are distinct features of substorm auroras composed of large-scale spirals (100s km Surges) mixed with smaller scale ones (10s km Folds, and 1 km Rays). Spiral patterns are generally interpreted in terms of the field line mapping of the upward field-aligned currents produced in the magnetosphere during the field line dipolarization. The field line mapping results in opposing spiral rotations of small- and large-scale auroras. Because of a rotational symmetry deformation and similarity in deformation speeds (6~8 km/s) of small- and large-scale spirals, it has been suggested that common physical processes may underlie the deforming processes. Internal processes in the polar ionosphere (ionospheric driver) will be proposed as the general dynamic for spiral auroras. The ionospheric driver rotated in the ionosphere to produce spirals that characteristically differ from the field line mapping scenario.