Symmetric Textures Research Articles

Particle–hole symmetry protects spin-valley blockade in graphene quantum dots

Particle-hole symmetry plays an important role in the characterization of topological phases in solid-state systems1. It is found, for example, in free-fermion systems at half filling and it is closely related to the notion of antiparticles in relativistic field theories2. In the low-energy limit, graphene is a prime example of a gapless particle-hole symmetric system described by an effective Dirac equation3,4 in which topological phases can be understood by studying ways to open a gap by preserving (or breaking) symmetries5,6. An important example is the intrinsic Kane-Mele spin-orbit gap of graphene, which leads to a lifting of thespin-valley degeneracy and renders graphene a topological insulator in a quantumspin Hall phase7 while preserving particle-hole symmetry. Here we show that bilayer graphene allows the realization of electron-hole double quantum dots that exhibit near-perfect particle-hole symmetry, in which transport occurs via the creation and annihilation of single electron-hole pairs with opposite quantum numbers. Moreover, we show that particle-hole symmetric spin and valley textures lead to a protected single-particle spin-valley blockade. The latter will allow robust spin-to-charge and valley-to-charge conversion, which are essential for the operation of spin and valley qubits.

A polynomial framework for design of drag reducing periodic two-dimensional textured surfaces

Periodic and symmetric two-dimensional textures with various cross-sectional profiles have been employed to improve and optimize the physical response of the surfaces such as drag force, superhydrophobicity, and adhesion. While the effect of the height and spacing of the textures have been extensively studied, the effect of the shape of the textures has only been considered qualitatively. Here, a polynomial framework is proposed to mathematically define the cross-sectional profiles of the textures and offer a quantitative measure for comparing the physical response of the textured surfaces with various shapes. As a case study, textured surfaces designed with this framework are tested for their hydrodynamic frictional response in the cylindrical Couette flow regime in Taylor–Couette flows. With the reduction in torque as the objective, experimental and numerical results confirm that textures with height-to-half-spacing ratios of lower and equal to unity with concave profiles offer a lower torque compared to both smooth surfaces and triangular textures. In addition, across multiple polynomial orders, textures defined by second-order polynomials offer a wide range of responses, eliminating the need for considering polynomials of higher orders and complexity. While the case study here is focused on the laminar flow regime and the frictional torque, the same type of analysis can be applied to other surface properties and physical responses as well.

Yield strength of CeO2 measured from static compression in a radial diamond anvil cell

Cerium oxide (ceria, CeO2) is frequently used as a standard in applications such as synchrotron and x-ray free electron lasers for calibrating x-ray wavelengths and offers the potential for understanding the high pressure properties and deformation mechanisms in a wide range of similar face centered cubic (fcc) materials. In this study, the pressure dependence of the strength of ceria was investigated up to 38 GPa using angle dispersive x-ray diffraction in a radial geometry in a diamond anvil cell. In this experiment, the difference in the stress along the axis of compression and perpendicular to the direction of compression can be determined, giving a quantity known as the differential stress. It was found that the differential stress (t), a measure of the lower bound for yield strength, initially increases rapidly from 0.35 ± 0.06 GPa to 2.2 ± 0.4 GPa at pressures of 1.8 and 3.8 GPa, respectively. Above 4 GPa, t increases more slowly to 13.8 ± 2.6 GPa at a pressure of 38 GPa. The changes in the preferred orientation (texture) of CeO2 with pressure were also measured, allowing for the determination of active deformation mechanisms using an elasto-viscoplastic self-consistent model (EVPSC). It was found that as pressure increased, the [001] direction had a slight preferred orientation along the axis of compression. Our EVPSC model of experimental fiber (cylindrically symmetric) textures and lattice strains were most consistent with dominant slip activity along {111}⟨11¯0⟩.

The design of metasurface based operator for conversion of orthogonal polarization

The operation of the polarization has always been the focus and hot point in the electromagnetic (EM) area. We propose the method to realize the operator for conversion of orthogonal polarization by metasurface with cascaded layers which concludes receiving antenna, polarization processing layer and transmitting antenna. The design of polarization processing layer located in the middle of the metasurface is core, and it can actualize the orthogonal manipulation by introducing the topological connection and phase inverter. Also, with applying the symmetric textures of receiving and transmitting antennas which are polarized insensitively, the total metasurface achieves the function of orthogonal polarization conversion under arbitrarily polarized states of incident wave. One sample of metasurface is fabricated and measured, and good agreement between simulation and measurement results is observed.

Néel-type antiferromagnetic skyrmionic crystals on two-dimensional square lattices investigated with optimized quantum Monte Carlo method

The formations of individual antiferromagnetic (AF) skyrmions and AF skyrmionic lattices on two-dimensional (2D) magnets with square crystal structure are debatable in recent years, for only an isolated skyrmion can be generated in such systems if classical Monte Carlo (CMC) method is employed. For the sake, we apply here an optimized quantum Monte Carlo approach to a 2D square magnet where the AF Heisenberg exchange (HE) and Dzyaloshinskii–Moriya (DM) interactions co-exist. Consequently, the computing program converges to the equilibrium states with appreciable computational speed, and the results obtained in the last one iteration are able to accurately produce well symmetric and periodic AF skyrmionic lattices (SLs) at elevated temperatures when a considerably strong external magnetic field is exerted perpendicular to the 2D monolayer. Moreover, each of these AF SLs can be decomposed into two almost identical ferromagnetic (FM) SLs, and the distribution of topological charge density also forms symmetric lattice with the same periodicity as the AF SL, dividing the AF SL into several areas of distinct spin configurations. The reasons why the OQMC approach can work beyond CMC method are explained in the Discussion Section. • Optimized Monte Carlo simulating method is described and applied here. • Results obtained in last loop can produce symmetric and periodical spin textures. • AF skyrmion crystals are generated in 2D square lattices with the method. • Each AF skyrmion crystal can be decomposed into two identical FM sub-lattices. • The topological charge density forms lattice almost identical with the spin texture.

Microstructure and Texture Evolution During Symmetric and Asymmetric Rolling of a Martensitic Ti-6Al-4V Alloy

In the current study, the effect of deformation mode (i.e., symmetric vs asymmetric rolling) on the extent of grain refinement and texture development in Ti-6Al-4V was examined through warm rolling of a martensitic starting microstructure. During rolling, the initial martensitic lath structure was progressively fragmented, primarily through continuous dynamic recrystallization. This eventually led to an ultrafine-grained (UFG) microstructure composed of equiaxed grains with a mean size of 180 to 230 nm, mostly surrounded by high-angle grain boundaries. Depending on the rolling reduction and deformation mode (symmetric and asymmetric), the rolled specimens displayed different layer morphologies throughout the specimen thickness: a fully UFG surface layer, a partial UFG transition layer, and a partially fragmented lath interior layer. Due to a higher level of effective strain and continuous rotation of the principle axis, asymmetric rolling resulted in a greater extent of grain refinement compared with symmetric rolling at a given thermomechanical condition. A bulk UFG structure was successfully obtained using 70 pct asymmetric rolling. In addition, the rolling texture exhibited various characteristics throughout the thickness due to a different combination of shear and compressive strains. Principally, the basal texture component was displaced from the normal toward rolling direction during asymmetric rolling, differing from the symmetric rolling textures.

Spin currents of exciton polaritons in microcavities with (110)-oriented quantum wells

We study the polarization optical properties of microcavities with embedded (110)-oriented quantum wells. The spin dynamics of exciton polaritons in such structures is governed by the interplay of the spin-orbit splitting of exciton states, which is odd in the in-plane momentum, and the longitudinal-transverse splitting of cavity modes, which is even in the momentum. We demonstrate the generation of polariton spin currents by linearly polarized optical pump and analyze the arising polariton spin textures in the cavity plane. Tuning the excitation spot size, which controls the polariton distribution in the momentum space, one obtains symmetric or asymmetric spin textures.

The hidden symmetries in the PMNS matrix and the light sterile neutrino(s)

The approximately symmetric form of the PMNS matrix suggests that there could exist a hidden symmetry which makes the PMNS matrix different from the CKM matrix for quarks. In literature, all the proposed fully symmetric textures exhibit an explicit [Formula: see text] symmetry in addition to other symmetries which may be different for various textures. Observing obvious deviations of the practical PMNS matrix elements from those in the symmetric textures, there must be a mechanism to distort the symmetry. It might be due to the existence of light sterile neutrinos. As an example, we study the case of the Tribimaximal (TB) texture and propose that its apparent symmetry disappears due to the existence of a sterile neutrino.

Textures on the surface of BSA films with different concentrations of sodium halides and water state in solution.

The formation of the textures on the surface of the films from the solutions of bovine serum albumin (BSA) with sodium halides (NaF, NaCl, and NaBr) of various concentrations was studied. The formation of symmetric zigzag textures on the surface of BSA films (Cryst Eng 3:173-194, 2000) in the presence of sodium halides depends on the conformational state of the protein globule. Thermal denaturation of BSA also did not allow to form zigzag textures on the surface of the films.

Magnetic ac control of the spin textures in a helical Luttinger liquid

We demonstrate the possibility to induce and control peculiar spin textures in a helical Luttinger liquid, by means of a time-dependent magnetic scatterer. The presence of a perturbation that breaks the time-reversal symmetry opens a gap in the spectrum, inducing single-particle backscattering and a peculiar spin response. We show that in the weak backscattering regime asymmetric spin textures emerge at the left and right sides of the scatterer, whose spatial oscillations are controlled by the ratio between the magnetization frequency and the Fermi energy and by the electron interaction. This peculiar spin response marks a strong difference between helical and nonhelical liquids, which are expected to produce symmetric spin textures even in the ac regime.

Topological Hall conductivity of vortex and skyrmion spin textures

We analyze the topological Hall conductivity experienced by conduction electrons whose spins are strongly coupled to axially symmetric spin textures, such as magnetic vortex and skyrmion of types I and II, theoretically by gauge theory, and numerically via micromagnetic simulations. The numerical results are in agreement with the theoretical predictions. Divergence between the two is seen when the vortex/skyrmion core radius is comparable or larger than the element size, and when the skyrmion configuration breaks down at high Dzyaloshinskii-Moriya interaction strength.

Study on perturbation schemes for achieving the real PMNS matrix from various symmetric textures

The PMNS matrix displays an obvious symmetry, but not exact. There are several textures proposed in literature, which possess various symmetry patterns and seem to originate from different physics scenarios at high energy scales. To be consistent with the experimental measurement, all of the regularities slightly decline, i.e. the symmetry must be broken. Following the schemes given in literature, we modify the matrices (9 in total) to gain the real PMNS matrix by perturbative rotations. The transformations may provide hints about the underlying physics at high energies and the breaking mechanisms which apply during the evolution to the low energy scale, especially the results may be useful for the future model builders.

Noise space decomposition method for two-dimensional sinusoidal model

The estimation of the parameters of the two-dimensional sinusoidal signal model has been addressed. The proposed method is the two-dimensional extension of the one-dimensional noise space decomposition method. It provides consistent estimators of the unknown parameters and they are non-iterative in nature. Two pairing algorithms, which help in identifying the frequency pairs have been proposed. It is observed that the mean squared errors of the proposed estimators are quite close to the asymptotic variance of the least squares estimators. For illustrative purposes two data sets have been analyzed, and it is observed that the proposed model and the method work quite well for analyzing real symmetric textures.

The software packageANAELUfor X-ray diffraction analysis using two-dimensional patterns

A new software package for interpreting two-dimensional diffraction diagrams is presented. The application capabilities include representation of single- and polycrystal structures with an inverse pole figure treatment of texture phenomena, measurement and analysis of diffraction signals, and different approaches to the modelling of two-dimensional diffraction patterns obtained from both single-crystal and polycrystalline samples. Particular consideration is given to the effect of axially symmetric textures on two-dimensional diffraction patterns. An example showing the capabilities of the software is presented.

Thermodynamics and mesoscopic organisation in Langmuir monolayers of an azobenzene derivative

We have carried out the analysis of liquid crystalline Langmuir monolayers at the air-water interface composed of the amphiphilic azobenzene derivative 8Az5COOH. By varying the temperature and the isomeric (trans-cis) composition, the monolayer behaviour has been studied in comparison with a shorter homologue, 8Az3COOH, by measuring the surface pressure-area isotherms along with Brewster angle microscopy (BAM). Our data with the pure trans isomer enable a posterior thermodynamic analysis, which was not feasible with the shorter homologue. For the mixed trans-cis monolayers, BAM observations reveal a phase segregation with trans enriched domains surrounded by a cis enriched matrix. Line tension between the two phases is lower than in the shorter homologue. The organisation of the rodlike molecules inside the trans domains results in highly symmetric textures that make the quantitative analysis of the BAM images possible, and a better understanding of the microscopic structure of the monolayer can be achieved.

LeptonicCPviolation induced by approximatelyμ-τsymmetric seesaw mechanism

Assuming a minimal seesaw model with two heavy neutrinos ($N$), we examine effects of leptonic $CP$ violation induced by approximate $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetric interactions. As long as $N$ is subject to the $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetry, we can choose $CP$ phases of Dirac mass terms without loss of generality in such a way that these phases arise from $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetry breaking interactions. In the case that no phase is present in heavy neutrino mass terms, leptonic $CP$ phases are controlled by two phases $\ensuremath{\alpha}$ and $\ensuremath{\beta}$. The similar consideration is extended to $N$ blind to the $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetry. It is argued that $N$ subject (blind) to the $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetry necessarily describes the normal (inverted) mass hierarchy. We restrict ourselves to $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetric textures giving the tribimaximal mixing and calculate flavor neutrino masses to estimate $CP$-violating Dirac and Majorana phases as well as neutrino mixing angles as functions of $\ensuremath{\alpha}$ and $\ensuremath{\beta}$. Since $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ are generated by $\ensuremath{\mu}$-$\ensuremath{\tau}$ symmetry breaking interactions, the $CP$-violating Majorana phase tends to be suppressed and is found to be at most $\mathcal{O}(0.1)$ radian. On the other hand, the $CP$-violating Dirac phase tends to show a proportionality to $\ensuremath{\alpha}$ or to $\ensuremath{\beta}$.

Two categories of approximately [formula omitted] symmetric neutrino mass textures

We present ten phenomenologically viable neutrino mass textures, which are approximately μ – τ symmetric: two for the normal mass hierarchy, three for the inverted mass hierarchy, and five for the quasi-degenerate mass pattern. Each texture falls into two categories characterized by either sin θ 13 → 0 (referred to as (C1)), or sin θ 12 → 0 (referred to as (C2)) in the μ – τ symmetric limit, where θ 12 and θ 13 , respectively, stand for the ν e – ν μ and ν e – ν τ mixing angles. Our textures that depend on the signs of neutrino masses as well as on (C1) and (C2) are so constructed to satisfy general relations, which ensure that Δ m ⊙ 2 / Δ m atm 2 ( ≡ R ) ≪ 1 and sin 2 θ 13 ≪ 1 , where Δ m ⊙ 2 and Δ m atm 2 are neutrino mass differences squared, respectively, for solar and atmospheric neutrinos. Three textures are found to provide R ∼ sin 2 θ 13 .

Can Symmetric Texture Reproduce the Unitarity Triangle and mb/m ?

We study the SUSY SO(10) GUT with the symmetric two-zero textures of the quark/lepton mass matrix which realize the Georgi-Jarlskog relations in down-type quark and charged lepton masses. We show that the important constraints on such a framework come from the bottom-tau unification and the observed value of sin 2 beta, one of the angles in the CKM unitarity triangle. We investigate the symmetric two-zero textures assumed at the GUT scale by solving the MSSM renormalization group equations with right-handed neutrino threshold effects. Our results indicate that the value of tan (beta) over tilde is large and the representation of the Higgs field which couples to the third generation of left- and right-handed neutrinos is restricted by the bottom-tau unification condition. The textures with a vanishing 1-2 (and 2-1) element for up-type quarks and a vanishing 1-3 (and 3-1) element for down-type quarks are favored by the observed value of sin 2 beta.

What doesμ−τsymmetry imply about neutrino mixings?

The requirement of the mu-tau symmetry in the neutrino sector that yields the maximal atmospheric neutrino mixing is shown to yield either sin(\theta_{13})=0 (referred to as C1)) or sin(\theta_{12})=0 (referred to as C2)), where \theta_{12(13)} stands for the solar (reactor) neutrino mixing angle. We study general properties possessed by approximately mu-tau symmetric textures. It is argued that the tiny mu-tau symmetry breaking generally leads to cos(2\theta_{23}) \simsin(\theta_{13}) for C1) and cos(2\theta_{23}) \sim \Delta m^2_\odot/\Delta m^2_{atm}(\equiv R) for C2), which indicates that the smallness of cos(2\theta_{23}) is a good measure of the mu-tau symmetry breaking, where \Delta m^2_{atm} (\Delta m^2_\odot) stands for the square mass differences of atmospheric (solar) neutrinos. We further find that the relation R \sim sin^2(\theta_{13}) arises from contributions of O(sin^2(\theta_{13})) in the estimation of the neutrino masses (m_{1,2,3}) for C1), and that possible forms of textures are strongly restricted to realize sin^2(2\theta_{12})=O(1) for C2). To satisfy R \sim sin^2(\theta_{13}) for C1), neutrinos exhibit the inverted mass hierarchy, or the quasi degenerate mass pattern with | m_{1,2,3}| \sim O(\sqrt{\Delta m^2_{atm}}), and, to realize sin^2(2\theta_{12})=O(1) for C2), there should be an additional small parameter \eta whose size is comparable to that of the mu-tau symmetry breaking parameter \epsilon, giving tan(2\theta_{12}) \sim \epsilon/\eta with \eta \sim \epsilon to be compatible with the observed large mixing.

Texture properties affecting the accuracy of surface attitude judgements

Prior studies of the perception of surface shape and attitude from texture have focused on measuring the sensitivity of the visual system to the various geometric deformations induced by projection. Studies that examine variations in accuracy caused by spatial properties of the texture itself are fewer, and often confound multiple, potentially important properties. Here we examine the perception of surface attitude for a broad range of synthetic textures that may represent the types of structure encountered in the natural world. These stimuli allow us to isolate the respective roles of texels, spatial scale structure, discrete symmetries and regularity in the judgement of both the slant and tilt of textured surfaces. Texels, spatial scale structure and discrete symmetries were all found to play a role. Discrete rotational symmetries were found to be particularly important for accurate tilt estimation, likely mediated by skew symmetry and/or linear perspective cues. The operational range of viewing distances over which accurate attitude judgements can be made is greatly extended when texture structure is distributed over multiple scales. Small biases caused by variations in the spin of symmetric textures are observed and are consistent, at least qualitatively, with a Bayesian cue combination model previously proposed by Saunders and Knill (2001).