Transverse Splitting Research Articles

Nanophotonic-assisted precision enhancement of weak measurement using spin Hall effect of light

Abstract The spin Hall effect of light, i.e., the microscopic and spin-dependent transverse splitting of linearly polarized light into circular polarizations at an optical interface, has been considered as a promising candidate for high-precision measurement when combined with a weak measurement technique. However, in those previous demonstrations, the precision is determined by the interface of interest, hindering its versatility. Here, by leveraging the direct correlation of precision with the spin Hall shift, we propose nanophotonic-assisted approaches to increase the precision of the weak measurement by controlling the spin Hall effect of light at the target interface. The refractive index sensing of an isotropic medium is demonstrated as a proof of concept, in which the precision can be increased, in principle, to infinity by placing an index-below-unity slab in the vicinity of the target interface. Furthermore, a single-layer metasurface comprising two-dimensional subwavelength patterns is introduced as an experimentally favorable platform. This study lays the foundation for nondestructive and high-precision investigation of unknown parameters of interfaces and will find wide sensing applications in material science, medical engineering, and other interdisciplinary fields.

Assessment of Mechanical Properties for High-Temperature Sandstone in Coal Fire Area Based on Different Cooling Methods

The rocks in coal fire areas are often in high-temperature environments. The mechanical properties of rocks play an important role in mining and engineering disturbance, so we aim to study the static and dynamic properties of high-temperature sandstone in the coal fire zone under different cooling methods, and to evaluate the degree of thermal damage at different high temperatures. The mechanical properties and failure modes of two cooling methods (natural cooling and watering cooling) were analyzed. In addition, the influence of the longitudinal wave velocity (Vp) on the mechanical properties of the high-temperature sandstone was analyzed, and the composition of the high-temperature sandstone was tested by XRD method. Under two cooling conditions, the static and dynamic peak strength of sandstone increases continuously with the increase of longitudinal wave velocity (Vp), and reduces with the increase of heat-treated temperature, but the damage degree increases with the increase of the heat treatment temperature. In the Split Hopkinson Pressure Bar (SHPB) test, the dynamic compressive strength of naturally cooled sandstone is higher than that of water-cooled sandstone. The failure of natural cooling high-temperature sandstone mainly occurs “X-shape”, transverse splitting failure or breaks into pieces, but the watering cooling high-temperature sandstone presents transverse or longitudinal splitting failure.

A Discontinuous Galerkin Finite Element Method based axial SN for the 2D/1D transport method

The 2D/1D transport method is a prominent solver for the 3D Boltzmann equation due to its strong geometric capability. To pursue high accuracy, the discrete ordinate (SN) method for transport equation is a straightforward choice as the axial 1D solver instead of the traditional nodal expansion method (NEM) for diffusion equation. In practice, the axial SN solver is usually combined with the transverse leakage splitting method to deal with the negative source issue, which strongly affects the convergence of the 2D/1D method. However, transverse leakage splitting breaks the consistency of scalar fluxes between the 2D MOC and 1D SN equations. To solve this problem, a discontinuous Galerkin finite element method (DGFEM) for axial SN together with an improved 2D/1D transport approach is proposed in the present study to ensure that the scalar flux from the 1D axial solver is the same as that from the 2D solver. The accuracy, consistency and computational efficiency of the new scheme are evaluated using various well-known numerical problems, including heterogeneous assembly problem, KUCA benchmark, and C5G5-3D benchmark.

Enhancing Spin Coherence in Optically Addressable Molecular Qubits through Host-Matrix Control

Optically addressable spins are a promising platform for quantum information science due to their combination of a long-lived qubit with a spin-optical interface for external qubit control and readout. The ability to chemically synthesize such systems—to generate optically addressable molecular spins—offers a modular qubit architecture which can be transported across different environments and atomistically tailored for targeted applications through bottom-up design and synthesis. Here, we demonstrate how the spin coherence in such optically addressable molecular qubits can be controlled through engineering their host environment. By inserting chromium (IV)-based molecular qubits into a nonisostructural host matrix, we generate noise-insensitive clock transitions, through a transverse zero-field splitting, that are not present when using an isostructural host. This host-matrix engineering leads to spin-coherence times of more than 10 μs for optically addressable molecular spin qubits in a nuclear and electron-spin-rich environment. We model the dependence of spin coherence on transverse zero-field splitting from first principles and experimentally verify the theoretical predictions with four distinct molecular systems. Finally, we explore how to further enhance optical-spin interfaces in molecular qubits by investigating the key parameters of optical linewidth and spin-lattice relaxation time. Our results demonstrate the ability to test qubit structure-function relationships through a tunable molecular platform and highlight opportunities for using molecular qubits for nanoscale quantum sensing in noisy environments.Received 18 March 2022Revised 16 June 2022Accepted 1 July 2022DOI:https://doi.org/10.1103/PhysRevX.12.031028Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasChemical Physics & Physical ChemistryQuantum engineeringQuantum information processingSpintronicsQuantum InformationCondensed Matter, Materials & Applied Physics

Excited-state spin-resonance spectroscopy of V{}_{{{{{{{{rm{B}}}}}}}}}^{-} defect centers in hexagonal boron nitride

The recently discovered spin-active boron vacancy (V{}_{{{{{{{{rm{B}}}}}}}}}^{-}) defect center in hexagonal boron nitride (hBN) has high contrast optically-detected magnetic resonance (ODMR) at room-temperature, with a spin-triplet ground-state that shows promise as a quantum sensor. Here we report temperature-dependent ODMR spectroscopy to probe spin within the orbital excited-state. Our experiments determine the excited-state spin Hamiltonian, including a room-temperature zero-field splitting of 2.1 GHz and a g-factor similar to that of the ground-state. We confirm that the resonance is associated with spin rotation in the excited-state using pulsed ODMR measurements, and we observe Zeeman-mediated level anti-crossings in both the orbital ground- and excited-state. Our observation of a single set of excited-state spin-triplet resonance from 10 to 300 K is suggestive of symmetry-lowering of the defect system from D3h to C2v. Additionally, the excited-state ODMR has strong temperature dependence of both contrast and transverse anisotropy splitting, enabling promising avenues for quantum sensing.

Dynamic compressive properties and underlying failure mechanisms of selective laser melted Ti-6Al-4V alloy under high temperature and strain rate conditions

In this study, high speed impacting tests are systematically conducted on a split Hopkinson pressure bar device to investigate the strain rate and temperature dependence of dynamic compressive properties of Ti-6Al-4 V (TC4) fabricated by selective laser melting (SLM), the ranges of strain rate and temperature are 2000–6000/s and 25–650 ℃, respectively. The results reveal that the yield strength and ultimate compressive strength of the SLM-TC4 alloy increase with the increasing strain rate and the decreasing temperature, showing obvious strain rate and temperature sensitivities. The high speed impacting load intensifies the texture of the SLM-TC4 alloy significantly. Adiabatic shear band (ASB) is more likely to evolve at higher temperatures and strain rates, submicron equiaxed grains formed in the ASB and the surrounding area are mainly ascribed to the combination of dynamic recrystallization, deformation-induced twinning and transverse α-lath splitting. Within the ASB, grains with {0001} pole orientation are rotated by approximately 45° with respect to the shear direction, indicating that the recrystallized grains are able to reorient themselves to accommodate to the shear deformation. The findings in this work provide a theoretical basis to understand the deformation behavior and mechanism of SLM-TC4 alloy under impacting loads, thus is helpful to widen the application of SLM technique and products. • SLMed TC4 alloy has significant temperature and strain rate sensitivities. • Strain hardening and thermal softening cause instable plastic deformation of SLMed TC4. • Ultrafine grains within ASBs mainly due to the deformation twinning, α -lath splitting and DRX. • Dynamic impact loading enhances the texture intensity of the deformed samples. • Recrystallized grains within ASBs can reorient themselves to accommodate to the shear deformation.

Research on the effect of incident polarization phase on transverse spin splitting of reflected beam

In this work, the theoretical relationship model between the incident polarization phase and transverse spin splitting (TSS) shifts of photonic spin Hall effect (PSHE) is established. Based on the established model, the effect of the incident polarization phase on the TSS is systematically studied, and several characteristic laws are summarized. These findings can help people better understand PSHE. In addition, it is found that, no matter what the incident angle and polarization angle are, the TSS shift at polarization phase equal to ±90° is larger than that at other polarization phases. It can even reach several microns under certain incident angle and polarization angle, and is almost an order of magnitude larger than the usual TSS shift, which is generally tens to hundreds of nanometers. This provides a new way for enhancing PSHE. Furthermore, when the polarization phase is 90° or −90°, under a certain polarization angle, slightly adjust the polarization angle, the TSS shift will change sharply and its direction will be reversed. This interesting finding has great application value in the field of photon manipulation.

Excited-State Spectroscopy of Spin Defects in Hexagonal Boron Nitride.

A negatively charged boron vacancy (VB-) color center in hexagonal boron nitride has recently been proposed as a promising quantum sensor due to its excellent properties. However, the spin level structure of the VB- color center is still unclear, especially for the excited state. Here we measured and confirmed the excited-state spin transitions of VB- using an optically detected magnetic resonance (ODMR) technique. The zero-field splitting of the excited state is 2.06 GHz, the transverse splitting is 93.1 MHz, and the g factor is 2.04. Moreover, negative peaks in fluorescence intensity and ODMR contrast at the level anticrossing point were observed, and they further confirmed that the spin transitions we measured came from the excited state. Our work deepens the understanding of the excited-state structure of VB- and promotes VB--based quantum sensing applications.

Reaching the highest efficiency of spin Hall effect of light in the near-infrared using all-dielectric metasurfaces

The spin Hall effect of light refers to a spin-dependent transverse splitting of light at a planar interface. Previous demonstrations to enhance the splitting have suffered from exceedingly low efficiency. Achievements of the large splitting with high efficiency have been reported in the microwave, but those in the optical regime remain elusive. Here, an approach to attain the large splitting with high efficiency in the near-infrared is proposed and experimentally demonstrated at 800 nm by using a dielectric metasurface. Modulation of the complex transmission of the metasurface leads to the shifts that reach 10λ along with efficiencies over 70% under two linear polarizations. Our work extends the recent attempts to achieve the large and efficient spin Hall effect of light, which have been limited only to the microwave, to the optical regime.

Incident‐Polarization‐Independent Spin Hall Effect of Light Reaching Half Beam Waist

AbstractThe spin Hall effect of light (SHEL), a spin‐dependent transverse splitting of light at an optical interface, is intrinsically an incident‐polarization‐sensitive phenomenon. Recently, an approach to eliminate the polarization dependence by equalizing the reflection coefficients of two linear polarizations has been proposed, but is only valid when the beam waist is sufficiently larger than the wavelength. Here, it is demonstrated that an interface, at which the reflection coefficients of the two linear polarizations are the same and so are their derivatives with respect to the incident angle, supports the polarization‐independent spin Hall shift, even when the beam waist is comparable to the wavelength. In addition, an isotropic–anisotropic interface that exhibits the polarization‐independent spin Hall shift over the entire range of incident angles is presented. Monte‐Carlo simulations prove that spin Hall shifts are degenerate under any polarization and reach a half of beam waist under unpolarized incidence. An application of the beam‐waist‐scale SHEL as a tunable beam‐splitting device that is responsive to the incident polarization is suggested. The spin Hall shift that is independent of the incident polarization at any incident angle will facilitate a wide range of applications including practical spin‐dependent devices and active beam splitters.

Pull-through failure of crest-fixed steel claddings under combined wind and bushfire conditions

Cold-formed steel (CFS) roof and wall cladding systems are commonly used in Australia and around the world. The use of CFS claddings in bushfire prone areas is becoming more popular due to their non-combustibility and is recommended in the Australian standard AS3959 for construction in bushfire areas. However, severe fire events occur more frequently and in recent bushfire events, strong winds and fire–wind interactions have been observed. Thus, the behaviour of CFS claddings exposed to a combined action of fire and wind needs to be considered for the safe design of buildings in bushfire prone areas. In this study, a small-scale test set-up was developed and used to simulate the wind suction loading on crest-fixed CFS roof and wall claddings while also being exposed to elevated temperatures. Experiments were conducted on three commonly used 0.42 mm high strength (G550) CFS cladding profiles at ambient and elevated temperatures and their critical localised pull-through failures of the crests under the screw heads were investigated at increasing temperatures. The results showed that the failure mode of trapezoidal cladding profiles changed from a transverse splitting type to a localised dimpling type pull-through failure. They also showed different rates of reduction in the pull-through capacity with increasing temperatures and the type of cladding profile. This paper has proposed a suitable equation for the pull-through capacity reduction with increasing temperatures and made suitable recommendations in relation to the use of CFS cladding systems in bushfire prone areas.

Ge2Sb2Se4Te1-based spin-decoupled metasurface for multidimensional and switchable focusing in the mid-infrared regime

Metalens is an ultrathin flat optical device with a great potential for applications in spin-controlled nanophotonics. However, most advanced metalenses typically work at a single wavelength or one specific spin state of incident light, hindering their applications in practice. In the present work, we report three distinct spin-dependent metalenses based on the novel phase-change material of Ge2Sb2Se4Te1 (GSST), enabling multidimensional splitting and switchable manipulation capabilities. Such schemes are successfully realized due to synergizing propagation phase and specific PB phase together with deliberately selecting several anisotropic GSST nanofins that behave as half-wave plates for their constituent elements. In particular, the transverse spin-dependent splitting metalens (TSSM) is demonstrated to enable the left-circularly polarized (LCP) and right-circularly polarized (RCP) incidence to focus at opposite transverse offsets within a broadband width from 3750 to 4600 nm (20.2% of the bandwidth). The longitudinal spin-dependent splitting metalens (LSSM) realizes the longitudinal spin-dependent splitting performance along z-axis upon RCP and LCP incidence in a considerable bandwidth (from 3900 to 4900 nm, 23.8% of the bandwidth). While for the hybrid design, it is implemented to obtain transverse and longitudinal spin-dependent splitting simultaneously for LCP and RCP light. It should be emphasized that all of the proposed metalenses are proved to ensure continuous tunability and the switching of “ON” and “OFF” states in terms of focusing and splitting features upon λ0= 4200 nm by gradually converting Ge2Sb2Se4Te1 from the amorphous to crystalline state. Our results lay a solid basis for versatile potential applications such as optical imaging and communications, optical sensors, machine vision and so forth.

Micromechanical analysis of roller compaction process with DEM

This study applies the discrete element method (DEM) to the roller compaction process for the analysis of particle flow behavior, porosity distribution in the compaction zone and in the final ribbon, as well as the pressure distribution on rollers. The roller compaction setup was implemented utilizing a piston feeder and smooth roller surfaces. The parameters of the elastoplastic DEM contact model were calibrated by uniaxial compression tests, interparticle and wall shear tests. Finally, the simulation results were validated by micro-computed tomography measurements of porosity profiles of manufactured lactose ribbons. From performed studies, it was observed that the particles passing the smallest gap possess higher velocity than the roller surface, and peak pressure is reached before the smallest gap. Furthermore, due to lateral relaxation, the particles in the center of the ribbon are faster than on the walls. The lateral stress can act as a further possible reason for the transversal ribbon splitting.

Perfect transverse spin splitting by a single particle with bianisotropy

Transverse spin splitting is a novel optical phenomenon which stems from the spin-orbit interaction of light. In this paper, we reveal the perfect transverse spin splitting in the scattered far-field of a single particle with bianisotropy. It is the result of the polarization twist effect caused by the omega-type bianisotropy of the structure in which the magnetic and electric fields interact in an unusual way and form a transverse spin dipole moment. Based on the dipole model, we conducted a detailed theoretical analysis of the relationship between the magnetoelectric coupling and the polarization state of the scattered far field. Our method reveals a physical mechanism of splitting the spin state of incident light which is regarded as a kind of giant spin Hall effect. Moreover, this perfect transverse spin splitting can also be understood by the separation of far-field polarization singularities. Our results provide a new platform for manipulating the spin state in the scattered far field and open an avenue for designing the spin structure.

Spin Hall Effect under Arbitrarily Polarized or Unpolarized Light

AbstractThe spin Hall effect of light (SHEL), which refers to a spin‐dependent and transverse splitting of refraction and reflection phenomena, inherently depends on the polarization states of incidence. Most previous research has focused on horizontally or vertically polarized incidence, in which the analytic expressions of the shift are well‐formulated and the SHEL appears symmetrically in both shift and intensity. However, the SHEL under arbitrarily polarized or unpolarized incidence has remained largely unexplored. Here, it is proved analytically and numerically that the SHEL is independent of the incident polarization and is symmetrical in shift if the two linear polarization states have the same Fresnel coefficients. Moreover, under an unpolarized incidence composed of a large number of completely random polarization states, the reflected beam is split in half into two circularly polarized components that undergo the same amount of splitting but in opposite directions. This result demonstrates that under unpolarized incidence, the SHEL occurs exactly as it does under horizontally or vertically polarized incidence. It is believed that the incident‐polarization‐independent SHEL can broaden the applicability of the SHEL to cover optical systems in which the polarization is unspecified.

Interference of exciton-polariton waves in GaSe nanocrystals

Absorption, reflection, photoluminescence and wavelength modulation transmission spectra of GaSe single crystals were investigated in temperature rage 300 – 10 K. From fitting of contours of excitonic reflection spectra parameters of excitons as energy of transversal exciton ω0 = 2.1212 eV, longitudinal transversal splitting ωLT = 2.3 meV, effective mass M = 2.5m0, background permittivity εb= 5.2 and damping constant γ = 1.4 were determined. Effective masses of electrons (mC1 = 0.37m0) and holes (mV1 = 2.13m0) in the Brillouin zone center were estimated. An interference of waves of upper and lower branches of exciton-polaritons was found out in wavelength modulation transmission spectra of GaSe nanocrystals.

Prediction of anomalous LA-TA splitting in electrides

Electrides are an emerging class of materials with excess electrons localized in interstices and acting as anionic interstitial quasi-atoms (ISQs). The spatial ion–electron separation means that electrides can be treated physically as ionic crystals, and this unusual behavior leads to extraordinary physical and chemical phenomena. Here, a completely different effect in electrides is predicted. By recognizing the long-range Coulomb interactions between matrix atoms and ISQs that are unique in electrides, a nonanalytic correction to the forces exerted on the matrix atoms is proposed. This correction gives rise to a longitudinal acoustic-transverse acoustic splitting in the acoustic branch of lattice phonons near the zone center, similar to the well-known longitudinal optical–transverse optical splitting in the phonon spectra of ionic compounds. The factors that govern this splitting are investigated, with isotropic fcc-Li and anisotropic hP4-Na as the typical examples. It is found that not all electrides can induce a detectable splitting, and criteria are given for this type of splitting. The present prediction unveils the rich phenomena in electrides and could lead to unprecedented applications.

Wies procedure for correcting involutional entropion of the lower lid in geriatrics

Objective: To evaluate the anatomic outcome and recurrence rate of the Wies procedure for treating involutional entropion of the lower lid in geriatrics.
 Materials and methods: This retrospective case series was conducted in the Ophthalmology department of a tertiary care hospital from January 1, 2016 to December 31, 2017. Geriatric patients (≥ 65 years) who had undergone the Wies procedure, i.e., transverse lid split and everting sutures for correction of involutional entropion of the lower lid were included. All the surgeries were done under local anaesthesia by a single ophthalmologist. The follow-up period was 12 months. A successful outcome was defined as restoration of lid margin to its position with no lash touching the cornea and no recurrence within 12 months.
 Results: Eighteen eyes of 13 patients with a mean age of 67.6 ± 2.2 SD years were included. There were 11 males (61%) and 7 females (39%). Bilateral entropion correction was done in five patients. Nine right eyes and nine left eyes were included. Anatomical success was 94.4% at 12 months. Recurrence was seen in one (5.6%) patient at 12 months.
 Conclusion: The Wies procedure for correction of involutional entropion with horizontal lid laxity in the geriatric population provided good anatomic results in our study. The recurrence rate was minimal within 1 year. The recurrence rate can be reduced by an accurate initial entropion assessment.

Underpinned exploration for magnetic structure, lattice dynamics, electronic properties, and disproportionation of yttrium nickelate

Magnetic behavior and disproportionation effect of nickelates are closely related to the nature of their ground state. In the present work, the magnetic structure, lattice dynamics, electronic properties, and disproportionation effect of yttrium nickelate (YNiO3) in its ground state P21/n structure were investigated by first-principles and phonon calculations based on density functional theory (DFT). The strong correlated interactions were treated by the DFT + U approach and the meta-generalized-gradient approximation approach implemented under the strongly constrained appropriately normed functional. The S-type antiferromagnetic insulating ground state of YNiO3 was captured well by both approaches. The disproportionation effect is quantitatively characterized through the Born effective charge, indicating the ligand-hole picture of Ni2+ → Ni2−δ+ Ni2+δ with δ = 0.3. The predicted phonon frequency at the Γ point agrees well with the measured value from infrared experiments, including the longitudinal and transverse optical splitting. The analysis based on stretching force constants indicated that the interaction between Ni and O atoms in the small nonmagnetic NiO6 octahedral clusters is stronger than that in the large magnetic NiO6 octahedral clusters.

Transitional Channel Flow: A Minimal Stochastic Model.

In line with Pomeau’s conjecture about the relevance of directed percolation (DP) to turbulence onset/decay in wall-bounded flows, we propose a minimal stochastic model dedicated to the interpretation of the spatially intermittent regimes observed in channel flow before its return to laminar flow. Numerical simulations show that a regime with bands obliquely drifting in two stream-wise symmetrical directions bifurcates into an asymmetrical regime, before ultimately decaying to laminar flow. The model is expressed in terms of a probabilistic cellular automaton of evolving von Neumann neighborhoods with probabilities educed from a close examination of simulation results. It implements band propagation and the two main local processes: longitudinal splitting involving bands with the same orientation, and transversal splitting giving birth to a daughter band with an orientation opposite to that of its mother. The ultimate decay stage observed to display one-dimensional DP properties in a two-dimensional geometry is interpreted as resulting from the irrelevance of lateral spreading in the single-orientation regime. The model also reproduces the bifurcation restoring the symmetry upon variation of the probability attached to transversal splitting, which opens the way to a study of the critical properties of that bifurcation, in analogy with thermodynamic phase transitions.