Stripe Structure Research Articles

Rescattering time-energy analysis of high-order above-threshold ionization in few-cycle laser fields

A Wigner distributionlike function based on the improved strong-field approximation theory is proposed to calculate the rescattering time-energy distribution (RTED) of high-energy photoelectrons of atomic above-threshold ionization process in few-cycle laser fields with different frequencies. The RTED shows bell-like stripes and the outermost stripe is compared with semiclassical results given by the simple-man model with consideration of different positions of tunnel exit and different initial longitudinal momenta. Analysis indicates the existence of the tunnel exit. However, though it shifts farther away from the core with decreasing frequency, the position of the tunnel exit is significantly less than the prediction by adiabatic theory even for the low-frequency case which is well in the tunneling regime. Our results also imply that the effect of the tunnel exit is more important than that of the initial longitudinal momentum at the tunnel exit for the backward-scattering electrons. Moreover, the inner stripe structures in the RTED are attributed to interference between electrons with the same final energy emitted at different ionization times.

Density structures and giant vortex in spin-orbit coupled Bose-Einstein condensates with the harmonic-plus-radial potential

We study the ground-state properties of two-dimensional Bose-Einstein condensate with spin-orbit coupling (SOC) loaded in the harmonic-plus-radial potential. In the immiscible regime, odd-petal-number states can be found. By increasing the effective atom interactions, the odd-petal-number states transform into a phase where petals in the outer annular potential trough are coexisting with inner longitudinal stripes, and finally become the ‘serpentine’ stripe structures. In a rotating system, the giant vortex (GV) can be stabilized and controllable. The favorable conditions for GV are relatively small atom interactions, intermediate rotation frequency and intermediate SOC strength. Further, this type of harmonic-plus-radial trapping with a strong radial part is a suitable choice to create GV state.

Investigation on halide vapor phase epitaxial growth of AlN using N2 as N source

Abstract Epitaxial growth of AlN films on sapphire substrates prepared by halide vapor phase epitaxy (HVPE) using N2 as N source is reported. The effects of V/III ratio on the growth rate, surface morphology and crystal quality of AlN films are systematically investigated. Compared with traditional HVPE using NH3 as N source, the growth rate of AlN films here increased linearly instead of decrease exponentially as increasing input V/III ratio. The surface morphology of the as-grown AlN films exhibited a periodic stripe structure at low V/III ratio and exhibited a pit-like or grid-like structure at high V/III ratio. The effect of V/III ratio on crystal quality varied under different HCl flow rate. The full width at half maximum (FWHM) of the (0002)- and (10-12)- plane X-ray rocking curves (XRCs) were 108–480 and 495–1083 arcsec, respectively, depending on both the V/III ratio and the growth rate of AlN films.

Multivalley Free Energy Landscape and the Origin of Stripe and Quasi-Stripe CDW Structures in Monolayer MX2 Compounds

Ultrathin sheets of transition metal dichalcogenides (MX2) with charge density waves (CDWs) is increasingly gaining interest as a promising candidate for graphene-like devices. Although experimental data including stripe/quasi-stripe structure and hidden states have been reported, the ground state of ultrathin MX2 compounds and, in particular, the origin of anisotropic (stripe and quasi-stripe) CDW phases is a long-standing problem. Anisotropic CDW phases have been explained by Coulomb interaction between domain walls and inter-layer interaction. However, these models assume that anisotropic domain walls can exist in the first place. Here, we report that anisotropic CDW domain walls can appear naturally without assuming anisotropic interactions: We explain the origin of these phases by topological defect theory (line defects in a two-dimensional plane) and interference between harmonics of macroscopic CDW wave functions. We revisit the McMillan-Nakanishi-Shiba model for monolayer 1T-TaS2 and 2H-TaSe2 and show that CDWs with wave vectors that are separated by 120° (i.e. the three-fold rotation symmetry of the underlying lattice) contain a free-energy landscape with many local minima. Then, we remove this 120° constraint and show that free energy local minima corresponding to the stripe and quasi-stripe phases appear. Our results imply that Coulomb interaction between domain walls and inter-layer interaction may be secondary factors for the appearance of stripe and quasi-stripe CDW phases. Furthermore, this model explains our recent experimental result (appearance of the quasi-stripe structure in monolayer 1T-TaS2) and can predict new CDW phases, hence it may become the basis to study CDW further. We anticipate our results to be a starting point for further study in two-dimensional physics, such as explanation of “Hidden CDW states”, study the interplay between supersolid symmetry and lattice symmetry, and application to other van der Waals structures.

X-band metamaterial absorbers based on reduced graphene oxide-silicon carbide-linear low density polyethylene composite

Graphene oxide obtained by Hummer's method is used to synthesize reduced graphene oxide (RGO) using chemical and thermal treatment method. Flexible composites of RGO-Silicon carbide (SiC)-Low density polyethylene (LLDPE) in different wt.% ratios of fillers are characterized for complex permittivity and permeability in X-band. A metamaterial design of ring shaped with four stripe structure is designed on developed substrate as well as standard FR4 substrate and simulated using EM simulator, CST Microwave Studio. Simulated results showed shifting of resonant peak frequency from C-band frequency for FR4 substrate to X-band for developed substrates signifying a role of microwave constitutive properties of the dielectric spacer. The fabricated metamaterial structure on RGO-SiC-LLDPE composite of thickness 0.7 mm shows a S11 ∼ −25 dB at 10.7 GHz with maximum absorption of 96.7%. Thus, the developed meta-material design showing a potential application in microwave applications.

Thermodynamics of the formation of surface PtO2 stripes on Pt(111) in the absence of subsurface oxygen.

This paper examines the thermodynamics of PtO2 stripes formed as intermediates of Pt(111) surface oxidation as a function of the degree of dilation parallel to the stripes, using density functional theory and atomistic thermodynamics. Internal energy calculations predict 7/8 and 8/9 stripe structures to dominate at standard temperature and pressure, which contain 7 or 8 elevated PtO2 units per 8 or 9 supporting surface Pt atoms, respectively. Moreover, we found a thermodynamic optimum with respect to mean in-stripe Pt-Pt spacing close to that of α-PtO2. Vibrational zero point energies, including bulk layer contributions, make a small but significant contribution to the stripe free energies, leading to the 6/7 stripe being most stable, although the 7/8 structure is still close in free energy. These findings correspond closely to experimental observations, providing insight into the driving force for oxide stripe formation and structure as the initial intermediate of platinum surface oxidation, and aiding our understanding of platinum catalysts and surface roughening under oxidative conditions.

Laser-induced damage and periodic stripe structures of a CaF2 single crystal by an ArF excimer laser

The laser-induced damage threshold of a calcium fluoride (CaF2) single crystal was obtained by a 193 nm ArF excimer laser. The damage morphology of the crystal was analyzed. The results showed that the surface of CaF2 single crystal broke along the natural cleavage plane under ArF excimer laser irradiation, some fragments fell off, and Newton’s rings were observed on the curved fragments. Laser-induced periodic stripe structures (LIPSS) appeared on the surface layer beneath the fragments that peeled off. The spacing of LIPSS was measured, and the formation mechanism of LIPSS was analyzed based on the interference model.

Femtosecond laser pulse ablation characteristics of polymer-derived SiAlCN ceramics

Polymer-derived ceramics (PDCs) are promising high-performance materials for various applications, yet their brittleness represents major drawback in their machining. Femtosecond laser pulse ablation is non-contact rapid processing method used in precision machining of PDCs. Herein, two laser parameters (laser energy fluence and rotational speed) were investigated to achieve laser–material interactions and machining characteristics via machine single circular lines, blind holes, and through-holes in polymer-derived SiAlCN ceramics. With the decrease in rotational speed, the morphology of single circular lines gradually roughened and heat-affected zone was produced. Varying ablation rates were obtained at different energy fluences. For blind holes, three different ablation regions were observed. As the energy fluence increased, blind holes gradually transformed into through-holes. Through-holes with near-cylindrical profiles and minimal collateral damage were obtained. Ablation debris deposited around through-holes were indicative of N release, breaking of Si–N and C–C bonds, and formation of SiOx. Laser ablation of PDCs led to the formation of laser-induced surface structures, bubble pits, stripe structures, molten materials, and sphere-like particles.

Guiding of LIPSS formation by excimer laser irradiation of pre-patterned polymer films for tailored hierarchical structures

LIPSS (Laser Induced Periodic Surface Structures) formation at pre-patterned photoresist films was investigated using a partial polarized excimer laser beam (λ = 248 nm, tp = 20 ns). These line and dot pre-patterns were fabricated by the lithography in a photoresist films and have widths of 1–3 µm and 1–5 µm, respectively. LIPSS with a period of 195 nm and a direction along the laser polarization were formed at very low laser fluences (threshold 7 mJ/cm2) and high pulse numbers. With increasing fluence first LIPSS appear at the top surface, extend than to the sidewalls and finally at fluences higher than (F ∼ 17 mJ/cm2) found only at the sidewalls while the top surface is smooth. The height of the LIPSS increases with the pulse number and saturates at approximately 65 nm. The degree of LIPSS order depends on the alignment of the laser polarization to the pattern direction and shape. For parallel alignment of polarization and pattern edges, a high degree of order was found over several hundreds of micrometers along the stripe structure. This order mechanism can accept alignment mismatches up to 10°. This approach may serve as a general guideline for forming well-ordered LIPSS on large areas.

Enabling the multifunctionality of thin films through complex engineered nanoscale phases/nanodomains

BiFeO3 is one of the most promising multiferroic material exhibiting, however, drawbacks as low dielectric susceptibility, poor chemical stability and high dielectric loss. Recently, we have demonstrated that joining doping and epitaxial strain engineering a nanoscale stripe structure was induced, resulting in a significant improvement of the dielectric characteristics. By high resolution transmission electron microscopy (HR-TEM) we have evidenced nanostripe domains with alternating compressive and tensile strain in the Y-doped BiFeO3 epitaxial thin films. Small band gap values of bismuth ferrite (BFO) have triggered the interest due to the photovoltaic and photocatalytic potential, for pure or cation doped BFO. However, energy related properties of BiFeO3 can be improved by coupling the strong ferroelectricity of BFO with chemical stability and small band gap value of LaFeO3 within thickness graded heterostructures. Thin films of BFO on 5-20 nm thick epitaxial LFO films deposited on different strain-induced substrates, have been obtained by RHEED- assisted Pulsed Laser Deposition. Their functional dielectric, optical and photolytic behaviour has been unravelled in connexion with complex ensembles of nanoscale phase/nanodomain fluctuations within the epitaxial films.

Visualizing the charge order and topological defects in an overdoped (Bi,Pb)2Sr2CuO6+x superconductor

Electronic charge order is a symmetry breaking state in high-$T_\mathrm{c}$ cuprate superconductors. In scanning tunneling microscopy, the detected charge-order-induced modulation is an electronic response of the charge order. For an overdoped (Bi,Pb)$_2$Sr$_2$CuO$_{6+x}$ sample, we apply scanning tunneling microscopy to explore local properties of the charge order. The ordering wavevector is non-dispersive with energy, which can be confirmed and determined. By extracting its order-parameter field, we identify dislocations in the stripe structure of the electronic modulation, which correspond to topological defects with an integer winding number of $\pm 1$. Through differential conductance maps over a series of reduced energies, the development of different response of the charge order is observed and a spatial evolution of topological defects is detected. The intensity of charge-order-induced modulation increases with energy and reaches its maximum when approaching the pseudogap energy. In this evolution, the topological defects decrease in density and migrate in space. Furthermore, we observe appearance and disappearance of closely spaced pairs of defects as energy changes. Our experimental results could inspire further studies of the charge order in both high-$T_\mathrm{c}$ cuprate superconductors and other charge density wave materials.

Quantum criticality of the transverse-field Ising model with long-range interactions on triangular-lattice cylinders

To gain a better understanding of the interplay between frustrated long-range interactions and zero-temperature quantum fluctuations, we investigate the ground-state phase diagram of the transverse-field Ising model with algebraically-decaying long-range Ising interactions on quasi one-dimensional infinite-cylinder triangular lattices. Technically, we apply various approaches including low- and high-field series expansions. For the classical long-range Ising model, we investigate cylinders with an arbitrary even circumference. We show the occurrence of gapped stripe-ordered phases emerging out of the infinitely-degenerate nearest-neighbor Ising ground-state space on the two-dimensional triangular lattice. Further, while cylinders with circumferences $6$, $10$, $14$ et cetera are always in the same stripe phase for any decay exponent of the long-range Ising interaction, the family of cylinders with circumferences $4$, $8$, $12$ et cetera displays a phase transition between two different types of stripe structures. For the full long-range transverse-field Ising model, we concentrate on cylinders with circumference four and six. The ground-state phase diagram consists of several quantum phases in both cases including an $x$-polarized phase, stripe-ordered phases, and clock-ordered phases which emerge from an order-by-disorder scenario already present in the nearest-neighbor model. In addition, the generic presence of a potential intermediate gapless phase with algebraic correlations and associated Kosterlitz-Thouless transitions is discussed for both cylinders.

Directional massless Dirac fermions in a layered van der Waals material with one-dimensional long-range order

One or a few layers of van der Waals (vdW) materials are promising for applications in nanoscale electronics. Established properties include high mobility in graphene, a large direct gap in monolayer MoS2, the quantum spin Hall effect in monolayer WTe2 and so on. These exciting properties arise from electron quantum confinement in the two-dimensional limit. Here, we use angle-resolved photoemission spectroscopy to reveal directional massless Dirac fermions due to one-dimensional confinement of carriers in the layered vdW material NbSi0.45Te2. The one-dimensional directional massless Dirac fermions are protected by non-symmorphic symmetry, and emerge from a stripe-like structural modulation with long-range translational symmetry only along the stripe direction as we show using scanning tunnelling microscopy. Our work not only provides a playground for investigating further the properties of directional massless Dirac fermions, but also introduces a unique component with one-dimensional long-range order for engineering nano-electronic devices based on heterostructures of vdW materials.

Fabrication of ZnSe/InP Heterojunctions on Flat and Shaped Surfaces of InP Laser Crystals

We have studied the growth of zinc selenide layers on flat and shaped indium phosphide surfaces. The growth rate of zinc selenide has been shown to depend on substrate orientation. It has been shown that the present results can be useful in designing mesa stripe structures for quantum electronic instruments. We have fabricated mesa stripe laser diodes operating on the absorption band of methane and suitable for producing fiber-optic signal transmission systems.

Effect of miR-26a on diabetic rats with myocardial injury by targeting PTEN.

To investigate the effect of micro ribonucleic acid (miR)-26a on diabetes-induced myocardial injury in rats by targeting the gene of phosphate and tension homology detected on chromosome ten (PTEN). Male Wistar rats aged 8-9 weeks old were divided into the control group (n=10), GK group (n=10), and miR-26a agomir group (n=10) according to the body weight. MiRanda and TargetScan target gene prediction software were used to predict and analyze the target gene of miR-26a-5p. The expressions of miR-26a and PTEN in the myocardial tissues of the diabetic rats were detected by quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). Hematoxylin-eosin (HE) staining was adopted to observe the pathological changes in the myocardial tissues. In addition, the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was conducted to detect myocardial apoptosis, while the expression of PTEN protein was detected via immunohistochemistry, and the protein expressions of PTEN, b-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and cysteinyl aspartate specific proteinase-3 (Caspase-3) were tested by Western blotting. TargetScan database analysis results showed that miR-26a-5p and PTEN 3'UTR had 6 pairs of complementary bases with the same sequence. Compared with those in the control group, the messenger RNA (mRNA) expression of PTEN in the GK group was notably increased (p<0.05), while that of miR-26a was substantially reduced (p<0.05). In comparison with those in the GK group, the mRNA expression of PTEN was significantly decreased, but that of miR-26a was significantly raised in miR-26a agomir group (p<0.05). Through observation under an optical microscope, it was manifested that in the control group, the myocardial fibers were intact with clear texture but no fracture, and the solid necrosis did not appear in myocardial cells. In the GK group, the myocardial fibers were disorderedly arranged and incomplete with an unclear edge and burrs. The myocardial fibers in the miR-26a agomir group were more regular, with less breakage and solid necrosis. According to TUNEL staining results, the TUNEL-stained brown granules in rats in the GK group were remarkably increased, relative to the control group (p<0.05). Compared with the GK group, miR-26a agomir group had markedly decreased the TUNEL-stained brown particles (p<0.05). It was found in immunohistochemical results that PTEN protein was in lighter color after staining in the control group, with a clear myocardial cell stripe structure. Compared with that in control group, PTEN protein in the GK group was in deeper color after staining, and in comparison with that in the GK group, the color of PTEN protein in miR-26a agomir group became significantly lighter. Moreover, the Western blotting results demonstrated that, compared with those in the control group, the Caspase-3 and Bax protein expressions in the GK group were significantly raised, while Bcl-2 protein expression was notably reduced (p<0.05). Besides, in comparison with the GK group, miR-26a agomir group evidently elevated Caspase-3 and Bax protein expressions and a notably increased Bcl-2 protein expression (p<0.05). We showed that miR-26a can protect against myocardial injury in diabetic rats by regulating PTEN.

Stripe structures in phase separated magnetic oxides

We investigate the phase separated inhomogeneous charge and spin states in magnetic oxides. In particular, we study one dimensional harmonic waves and stripe structures. We show that harmonic spin charge waves are unstable and inevitably transform into two or three dimensional structures, while the stripe structures can be stable for certain parameters. Such stripe structures may allow the control of magnetic state with electric field in a magnetic oxide thin film.

463-P: Linagliptin Ameliorated Heart Damage Associated with the Suppression of Necroptosis in Type 1 Diabetic Mice

Background: In diabetic patients, the incident of heart failure is two to five times greater when compared to that of general population. The influence of DPP-4 inhibitor on the heart failure and cardiac damage in diabetes is not completely elucidated yet. Therefore, to understand the pathobiology of heart damage in diabetes and the influence of DPP-4 inhibitor is emerged as significant. Necroptosis, recently identified as programmed cell death, had shown to be involved in heart damage of ischemic heart disease model. Here we found that intervention with DPP-4 inhibitor linagliptin (LINA) ameliorated heart damage in diabetic mice associated with the suppression of necroptosis. Method: We utilized streptozotocin-induced diabetic CD-1 mice (STZ:200mg/kg). At 20 weeks after the onset of diabetes, diabetic mice were treated with LINA (STZ+LINA) for 4 weeks. Result: Blood pressure, blood glucose, body and heart weights were not different between STZ and STZ+LINA. Ultrasonic Echocardiography analysis revealed that LVDd and LVDs were significantly decreased in STZ and STZ+LINA compared with control. STZ-induced diabetic CD-1 mice exhibited perivascular fibrosis evaluated by picrosirius red staining and strong immunoreactivity for DPP-4 expression in cardiac interstitium; STZ+LINA exhibited suppression of DPP-4 and amelioration of heart fibrosis. Diabetic CD-1 mice exhibited deficiency in myocardial stripe structure and endothelial damage in electron microscopy; LINA normalized all. When necroptosis was evaluated by associated kinases, RIP3 and MLKL, diabetic CD-1 mice were exhibited a strong RIP3 and MLKL mRNA and protein expression levels in myocyte; LINA suppressed RIP3 and MLKL levels in myocyte. Conclusion: These results indicated that LINA restored cardiac structure associated with suppression of necroptosis in type 1 diabetic mice. Disclosure T. Hirai: None. Y. Takagaki: None. K. Kanasaki: Other Relationship; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Sanofi, Taisho Toyama Pharmaceutical. D. Koya: Research Support; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Mitsubishi Tanabe Pharma Corporation. Speaker's Bureau; Self; Astellas Pharma Inc., Astellas Pharma Inc., AstraZeneca, Merck &amp; Co., Inc., Mitsubishi Tanabe Pharma Corporation, Taisho Pharmaceutical Co., Ltd. Funding Japan Society for the Promotion of Science

Is There Any Hidden Symmetry in the Stripe Structure of Perovskite High-Temperature Superconductors?

Local and fast structural probes using synchrotron radiation have shown nanoscale striped puddles and nanoscale phase separation in doped perovskites. It is known that the striped phases in doped perovskites are due to competing interactions involving charge, spin, and lattice degrees of freedom. In this work, we show that two different stripes can be represented as a superposition of a pair of stripes, U(θ n) or D(θ n), characterized by perovskite tilts where one of the pair is rotated in relation to the other partner by an angle Δθ n = π/2. The spatial distribution of the U and D stripes is reduced to all possible maps in the well-known mathematical four-color theorem. Both the periodic striped puddles and random structures can be represented by using planar graphs with a chromatic number χ ≤ 4. To observe the colors in mapping experiments, it is necessary to recover variously oriented tilting effects from the replica. It is established that there is an interplay between the annihilation/creation of new stripes and ordering/disordering tilts in relation to the θ n angle in the CuO2 plane, where the characteristic shape of the stripes coincides with the tilting-ordered regions.

Formation of the quasi-regular stripe nanodomain structures in lithium tantalate by scanning laser heating

The domain structure formation in the congruent lithium tantalate single crystals after IR laser irradiation by linear scanning of Z + polar surface has been studied. Two types of domain structures have been revealed experimentally: self-similar structure and quasi-regular stripe structure. The statistical processing has shown that the increase in the scanning velocity leads to increase in the area with stripe domain structure and to decrease in the average domain period. At the maximum scanning velocity 4.8 m/s, the quasi regular domain stripe structure with average period 0.8 μm has been obtained over the 70% of the switched area.

Metastable hard-axis polar state of a spinor Bose-Einstein condensate under a magnetic field gradient

We investigate the stability of a hard-axis polar state in a spin-1 antiferromagnetic Bose-Einstein condensate under a magnetic field gradient, where the easy-plane spin anisotropy is controlled by a negative quadratic Zeeman energy $q<0$. In a uniform magnetic field, the axial polar state is dynamically unstable and relaxes into the planar polar ground state. However, under a field gradient $B'$, the excited spin state becomes metastable down to a certain threshold $q_{th}$ and as $q$ decreases below $q_{th}$, its intrinsic dynamical instability is rapidly recalled. The incipient spin excitations in the relaxation dynamics appear with stripe structures, indicating the rotational symmetry breaking by the field gradient. We measure the dependences of $q_{th}$ on $B'$ and the sample size, and we find that $q_{th}$ is highly sensitive to the field gradient in the vicinity of $B'=0$, exhibiting power-law behavior of $|q_{th}|\propto B'^{\alpha}$ with $\alpha \sim 0.5$. Our results demonstrate the significance of the field gradient effect in the quantum critical dynamics of spinor condensates.