Trilayer anisotropic structure versus randomly oriented structure in heart valve leaflet tissue engineering

It has been hypothesized that leaflet substrates with a trilayer structure and anisotropicmechanical properties could be useful for the production of functional and long-lasting tissue-engineered leaflets.To investigate the influence of the anisotropic structural and mechanical characteristics of a substrate on cells,in this study,we electrospun trilayer anisotropic fibrous substrates and randomly oriented isotropic fibrous substrates(used as controls)from polycaprolactone polymers.Consequently,the random substrates had higher radial and lower circumferential tensile properties than the trilayer substrates;however,they had similar flexural properties.Porcine valvular interstitial cells cultured on both substrates produced random and trilayer cell-cultured constructs,respectively.The trilayer cell-cultured constructs had more anisotropic mechanical properties,17%higher cellular proliferation,14%more extracellular matrix(i.e.,collagen and glycosaminoglycan)production,and superior gene and protein expression,suggesting that more cells were in a growth state in the trilayer constructs than in the random constructs.Furthermore,the random and radial layers of the trilayer constructs had more vimentin,collagen,transforming growth factor-beta 1(TGF-ß1),transforming growth factor-beta 3(TGF-ß3)gene expression than in the circumferential layer of the constructs.This study verifies that the differences in structural,tensile,and anisotropic properties of the trilayer and random substrates influence the characteristics of the cells and ECM in the constructs.

Spontaneous isospin polarization and quantum Hall ferromagnetism in a rhombohedral trilayer graphene superlattice

Moiré superlattices in van der Waals heterostructures have recently attracted enormous interests, due to the highly controllable electronic correlation that gives rise to superconductivity, ferromagnetism, and nontrivial topological properties. To gain a deep understanding of such exotic properties, it is essential to clarify the broken symmetry between spin and valley flavors which universally exists in these ground states. Here in a rhombohedral trilayer graphene crystallographically aligned with a hexagonal boron nitride, we report various kinds of symmetry-breaking transition tuned by displacement fields(D) and magnetic fields:(ⅰ) While it is well known that a finite D can enhance correlation to result in correlated insulators at fractional fillings of a flat band, we find the correlation gap emerges before the flavor is fully filled at a positive D, but the sequence is reversed at a negative D.(ⅱ) Around zero D, electronic correlation can be invoked by narrow Landau levels, leading to quantum Hall ferromagnetism that lifts all the degeneracies including not only spin and valley but also orbital degrees of freedom. Our result unveils the complication of transitions between symmetry-breaking phases, shedding light on the mechanisms of various exotic phenomena in strongly correlated systems.

Investigation on the magnetomechanical behavior of trilayered GM actuator

In this article, it was suggested a TbFe/Co/Dy trilayered GM （Giant Magnetostrictive） film type actuator and investigated the magnetomechanical characteristics of the actuator for micro application. The trilayered films were fabricated at different thickness ratios to get an optimized structure. TbFe had positive GM properties, and cobalt, dysprosium layers made the magnetostriction property of composite film increase in low magnetic field. To fabricate the Si based microactuator with trilayered film, micromachining processes including RIE （Reactive Ion Etching） and selective DC magnetron sputtering techniques were combined. The deposited film thicknesses were measured by X-ray diffraction （XRD）. As a result, the magnetization of the film on the fabricated actuator was observed to characterize the magnetic properties of the TbFe/Co/Dy film using VSM （Vibrating Sample Magnetometer）. The magnetostriction of the actuator was determined by measuring the differences of curvature of the film coated silicon substrates using the optical cantilever method, and the deflections were also estimated under the external magnetic field lower than 0.5T for micro-system applications.

Micromagnetic simulation of Sm–Co/α-Fe/Sm–Co trilayers with various angles between easy axes and the film plane

Hysteresis loops and energy products have been calculated systematically by a three-dimensional （3D） software OOMMF for Sm-Co/α-Fe/Sm-Co trilayers with various thicknesses and β, where β is the angle between the easy axis and the field applied perpendicular to the film plane. It is found that trilayers with a perpendicular anisotropy possess considerably larger coercivities and smaller remanences and energy products compared with those with an in-plane anisotropy. Increase of β leads to a fast decrease of the maximum energy product as well as the drop of both remanence and coercivity. Such a drop is much faster than that in the single-phased hard material, which can explain the significant discrepancy between the experiment and the theoretical energy products. Some modeling techniques have been utilized with spin check procedures performed, which yield results in good agreement with the one-dimensional （1D） analytical and experimental data, justifying our calculations. Further, the calculated nucleation fields according to the 3D calculations are larger than those based on the 1D model, whereas the corresponding coercivity is smaller, leading to more square hysteresis loops and better agreement between experimental data and the theory.

Quantum spin Hall and quantum valley Hall effects in trilayer graphene and their topological structures

The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number Cs for energy-bands of trilayer graphene having the essence of intrinsic spin-orbit coupling is analytically calculated. We find that for each valley and spin, Cs is three times larger in trilayer graphene as compared to single layer graphene. Since the spin Chern-number corresponds to the number of edge states, consequently the trilayer graphene has edge states, three times more in comparison to single layer graphene. We also study the trilayer graphene in the presence of both electric-field and intrinsic spin-orbit coupling and investigate that the trilayer graphene goes through a phase transition from a quantum spin Hall state to a quantum valley Hall state when the strength of the electric field exceeds the intrinsic spin coupling strength. The robustness of the associated topological bulk-state of the trilayer graphene is evaluated by adding various perturbations such as Rashba spin-orbit （RSO） interaction αR, and exchange-magnetization M. In addition, we consider a theoretical model, where only one of the outer layers in trilayer graphene has the essence of intrinsic spin-orbit coupling, while the other two layers have zero intrinsic spin-orbit coupling. Although the first Chern number is non-zero for individual valleys of trilayer graphene in this model, however, we find that the system cannot be regarded as a topological insulator because the system as a whole is not gaped.

A Theoretical Analysis of Thermoelastic Damping Model in Laminated Trilayered Circular Plate Resonators

Thermoelastic damping of the axisymmetric vibration of laminated circular plate resonators is discussed in this paper. Based on the classical laminated plate theory assumptions, the governing equations of coupled thermoelastic problems are established for axisymmetric out-of-plane vibration of trilayered circular plate. The analytical expression for thermoelastic damping is obtained and the accuracy is verified through comparison with finite element analysis results. Then some simplifications are made on the theoretical model.

Quick identification of ABC trilayer graphene at nanoscale resolution via a near-field optical route

ABC-stacked trilayer graphene has exhibited a variety of correlated phenomena owing to its relatively flat bands and gate-tunable bandgap.However,convenient methods are still lacking for identifying ABC graphene with nanometer-scale resolution.Here we demonstrate that the scanning near-field optical microscope working in ambient conditions can provide quick recognition of ABC trilayer graphene with no ambiguity and excellent resolution(∼20 nm).The recognition is based on the difference in their near-field infrared(IR)responses between the ABA and ABC trilayers.We show that in most frequencies,the response of the ABC trilayer is weaker than the ABA trilayer.However,near the graphene phonon frequency(∼1585 cm−1),ABC’s response increases dramatically when gated and exhibits a narrow and sharp Fano-shape resonant line,whereas the ABA trilayer is largely featherless.Consequently,the IR contrast between ABC and ABA becomes reversed and can even be striking(ABC/ABA∼3)near the graphene phonon frequency.The observed near-field IR features can serve as a golden rule to quickly distinguish ABA and ABC trilayers with no ambiguity,which could largely advance the exploration of correlation physics in ABC-stacked trilayer graphene.

Trilayered Fibrous Dressing with Wettability Gradient for Spontaneous and Directional Transport of Massive Exudate and Wound Healing Promotion

Excessive exudate at wound sites increases treatment difficulty and severely decelerates the healing process.In wound exu-date management,dressings with unidirectional liquid transport capability have exhibited enormous potential.However,it remains challenging to improve the one-way liquid transport efficiency.Herein,a trilayered fibrous dressing is constructed by sequentially electrospinning polyurethane(PU)and polyvinylidene fluoride(PVDF)onto cotton fabric.Through hot pressing,a stable wettability gradient is formed across the PVDF/PU/cotton dressing due to the melting and bridging of PU nanofib-ers.The trilayered dressing exhibited rapid unidirectional transport with water penetrating from the hydrophobic side to the hydrophilic side in 6 s.The hydrostatic pressure from the hydrophilic side to the hydrophobic side is 569%higher than that from the hydrophobic side to the hydrophilic side,indicating that the dressing has a profound unidirectional conductivity.In vivo experiments demonstrates that the trilayered dressing can accelerate the wound healing process,especially in the early stages of wound occurrence,by quickly draining the excessive exudate.This study provides a new method to construct wound dressings with wettability gradients,which are advantageous for efficient exudate removal.

Contrasting physical properties of the trilayer nickelates Nd4Ni3O10 and Nd4Ni3O8

We report the crystal structures and physical properties of trilayer nickelates Nd4Ni3O10and Nd4Ni3O8.Measurements of magnetization and electrical resistivity display contrasting behaviors in the two compounds.Nd4Ni3O10shows a paramagnetic metallic behavior with a metal-to-metal phase transition(T^*)at about 162 K,as revealed by both magnetic susceptibility and resistivity.Further magnetoresistance and Hall coefficient results show a negative magnetoresistance at low temperatures and the carrier type of Nd4Ni3O10is dominated by hole-type charge carriers.The significant enhancement of Hall coefficient and resistivity below T*suggests that effective charge carrier density decreases when cooling through the transition temperature.In contrast,Nd4Ni3O8 shows an insulating behavior.In addition,this compound shows a paramagnetic behavior with the similar magnetic moment as that of Nd4Ni3O10derived from the Curie-Weiss fitting.This may suggest that the magnetic moments in both systems are contributed by Nd^3+ ions.By applying pressures up to about 49 GPa,the insulating behavior is still present and becomes even stronger under a high pressure.Our results suggest that the different Ni configurations(Ni^1+/2+ or Ni^2+/3+)and the changes of coordination environment of Ni sites may account for the contrasting behaviors in trilayer nickelates Nd4Ni3O10and Nd4Ni3O8.

Enhanced interlayer neutral excitons and trions in MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure

Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic devices.However,the bilayer heterostructure with type-II band alignment can only produce low quantum yield.Here,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of IXs.It is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation recombination.By analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was confirmed.Our results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.

Insight into the underlying competitive mechanism for the shift of the charge neutrality point in a trilayer-graphene field-effect transistor

Layer-number modulation in graphene has become a recent focus of research due to the superior degree of freedom that can be achieved in terms of magic-angle,wettability,superconductivity,and superlattices.However,the intrinsic transport of multilayer graphene is indistinguishable in atmospheric adsorbates and supporting environment,and its underlying charge transfer mechanism has not yet been thoroughly determined.In this study,a shift in the charge neutrality point of trilayer graphene(TLG)is demonstrated to be regulated by three governing factors:oxygen gas(O_(2)),water molecules(H_(2)O),and thermally activated electrons.Absorbed O_(2) induces a high work function in semimetallic TLG,while H_(2)O is not an evident dopant but can strengthen binding against O_(2) desorption.A simplified model is developed to elucidate the competitive mechanism and charge transfer among these two dopants(O_(2),H_(2)O)and thermal electrons,and the model is demonstrated by work function regulation and Bader charge transfer based on density functional theory calculations.This study provides a strategy to explore transport modulation of multilayer graphene in the fields of ballistic transport and low power consumption of graphene field-effect transistors.

Light-induced unconventional Landau levels of ultracold fermions in a trilayer honeycomb lattice

The spectrum of cold fermionic atoms is studied in a trilayer honeycomb optical lattice subjected to a perpendicular effective magnetic field,which is created with optical means. In the low energy approximation,the spectrum shows unconventional Landau levels,which are proportional to the 3/2 power of integer numbers. The zoro modes exist and the quasiparticles are chiral. It is also proposed to identify the unconventional Landau levels via probing the dynamic structure factor of the system with Bragg spectroscopy.

Lattice relaxation,mirror symmetry and magnetic field effects on ultraflat bands in twisted trilayer graphene

Twisted graphene multilayers exhibit strongly correlated insulating states and superconductivity due to the presence of ultraflat bands near the charge neutral point.In this paper,the response of ultraflat bands to lattice relaxation and a magnetic field in twisted trilayer graphene(tTLG)with different stacking arrangements is investigated by using a full tight-binding model.We show that lattice relaxations are indispensable for understanding the electronic properties of tTLG,in particular,of tTLG in the presence of mirror symmetry.Lattice relaxations renormalize the quasiparticle spectrum near the Fermi energy and change the localization of higher energy flat bands.Furthermore,different from the twisted bilayer graphene,the Hofstadter butterfly spectrum can be realized at laboratory accessible strengths of magnetic field.Our work verifies tTLG as a more tunable platform than the twisted bilayer graphene in strongly correlated phenomena.

Observation of interlayer excitons in trilayer type-Ⅱ transition metal dichalcogenide heterostructures

Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer excitons(IXs)can be generated in adjacent layers because of strong Coulomb interactions.However,due to the complexity of the multilayered heterostructure(HS),the capture and study of the IXs in trilayer type-Ⅱ HSs have so far remained elusive.Here,we present the observation of the IXs in trilayer type-Ⅱ staggered band alignment of MoS_(2)/MoSe_(2)/WSe_(2) van der Waals(vdW)HSs by photoluminescence(PL)spectroscopy.The central energy of IX is 1.33 eV,and the energy difference between the extracted double peaks is 23 meV.We confirmed the origin of IX through PL properties and calculations by the density functional theory,we also studied the dependence of the IX emission peak on laser power and temperature.Furthermore,the polarization-resolved PL spectra of HS were also investigated,and the maximum polarizability of the emission peak of WSe_(2) reached 11.40%at 6 K.Our findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.

High-magnetic-field tunneling spectra of ABC-stacked trilayer graphene

With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.He Lin(何林)at the Center for Advanced Quantum Studies,Department of Physics,Beijing Normal University,in collaboration with Prof.Yin LongJing(殷隆晶)at Hunan University,found interesting broken-symmetry states and many-body effects in the quantum Hall regime of the ABC-stacked trilayer graphene,which was published in Physical Review Letters(2019,122:146802).

Effect of Annealing on the Morphology,Structure and Photoelectric Properties of AZO/Pt/FTO Trilayer Films

Aluminum-doped zinc oxide/platinum/fluorine-doped tin oxide（AZO/Pt/FTO） trilayer films were prepared by sputtering 5-nm-thick Pt layers and 150-nm-thick AZO layers in sequence on commercial FTO glass.The effects of onestep annealing and layer-by-layer annealing on the morphology,structure and photoelectric properties of the AZO/Pt/FTO trilayer films were comparatively analyzed.It is found that the both annealing approaches increased the grain size and improved the crystallinity of the films,leading to enhancement in transmittance and conductivity.However,layer-by-layer annealing led to the formation of quasi-continuous or continuous AZO layers,different from the sparsely distributed AZO particles brought about by one-step annealing,resulting in excellent optical and electrical properties.Specifically,after layer-by-layer annealing at 400 ℃ for both Pt and AZO layers,the AZO/Pt/FTO trilayer film showed an increase in average transmittance from 71.3% to 85.3% and a decrease in sheet resistance from 7.5 to 5.6 Ω/□,leading to the highest figure of merit of 3.64 × 10^（-2） Ω^（-1）.

Integer quantum Hall effect in Kekulé-patterned graphene

Y-shaped Kekulébond textures in a honeycomb lattice on a graphene-copper superlattice have recently been experimentally revealed.In this paper,the effects of such a bond modulation on the transport coefficients of Kekulé-patterned graphene are investigated in the presence of a perpendicular magnetic field.Analytical expressions are derived for the Hall and longitudinal conductivities using the Kubo formula.It is found that the Y-shaped Kekulébond texture lifts the valley degeneracy of all Landau levels except that of the zero mode,leading to additional plateaus in the Hall conductivity accompanied by a split of the corresponding peaks in the longitudinal conductivity.Consequently,the Hall conductivity is quantized as±ne^(2)/h for n=2,4,6,8,10,...,excluding some plateaus that disappear due to the complete overlap of the Landau levels of different cones.These results also suggest that DC Hall conductivity measurements will allow us to determine the Kekulébond texture amplitude.

The rotational anisotropies in the ferromagnetism/antiferromagnetism 1/ antiferromagnetism 2 exchange bias structures

The rotational anisotropies in the exchange bias structures of ferromagnetism/antiferromagnetism 1/antiferro- magnetism 2 are studied in this paper. Based on the model, in which the antiferromagnetism is treated with an Ising mean field theory and the rotational anisotropy is assumed to be related to the field created by the moment induced on the antiferromagnetic layer next to the ferromagnetic layer, we can explain why in experiments for ferromag- netism （FM）/antiferromagntism 1 （AFM1）/antiferromagnetism 2 （AFM2） systems the thickness-dependent rotational anisotropy value is non-monotonic, i.e. it reaches a minimum for this system at a specific thickness of the first anti- ferromagnetic layer and exhibits oscillatory behaviour. In addition, we find that the temperature-dependent rotational anisotropy value is in good agreement with the experimental result.

Enhanced Spin Injection into ZnO Semiconductor Measured by Magnetoresistance

We prepare 2× （NiFe/CoZnO）/ZnO/（CoZnO/Co）×2 spin valve structures used for spin injection by sputtering and photolithography. In the junctions, the free magnetic layer 2× （NiFe/CoZnO） and the fixed magnetic layer （CoZnO/Co） × 2 are used to realize the spin valve functions in the external switch magnetic field. Since the wide gap semiconductor ZnO layer is located between the two magnetic semiconductor layers CoZnO, the electrical ,spin injection from the magnetic semiconductor CoZnO into the non-magnetic semiconductor ZnO is realized. Based on the measured magnetoresistance and the Schmidt model, the spin polarization ratio in the ZnO semiconductor is deduced to be 11.7% at 90K and 7.0% at room temperature, respectively.

Fabrication of rhenium Josephson junctions

Rhenium is a superconductor with a relatively weak tendency to oxidize, which is advantageous in superconducting quantum circuit and qubit applications. In this work, Re/A1-A1Ox/Re Josephson tunnel junctions were fabricated using a selective film-etching process similar to that developed in Nb trilayer technology. The Re films had a superconducting transition temperature of 4.8 K and a transition width of 0.2 K. The junctions were found to be highly reproducible using the fabrication process and their characteristics had good quality with a low leakage current and showed a superconducting gap of 0.55 meV.