# Artigos - Física - IGCE

URI Permanente para esta coleçãohttps://hdl.handle.net/11449/24972

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ItemArtigo A second order phase transition characterized in the suppression of unlimited chaotic diffusion for a dissipative standard mapping(2022-12-01) Miranda, Lucas Kenji Arima ; Moratta, Raphael ; Kuwana, Célia Mayumi ; Yoshida, Makoto ; de Oliveira, Juliano Antonio ; Leonel, Edson Denis ; Universidade Estadual Paulista (UNESP)An order parameter is identified in a dissipative standard mapping during the transition from limited to unlimited chaotic diffusion. The suppression of the unlimited chaotic diffusion is proved due to the existence of a continuous phase transition. The average squared action is obtained, allowing the investigation of the main properties of the transition for long-time dynamics (stationary state). The main questions to characterize the order of this phase transition are: (i) what is the order parameter; (ii) what is the elementary excitation of the dynamics affecting the transport of particles in the system?ItemArtigo Fractionalization of Majorana-Ising-type quasiparticle excitations(2023-04-15) Sanches, J. E. ; Lustosa, L. T. ; Ricco, L. S. ; Shelykh, I. A. ; De Souza, M. ; Figueira, M. S. ; Seridonio, A. C. ; Universidade Estadual Paulista (UNESP) ; University of Iceland ; Mipt ; Universidade Federal Fluminense (UFF)We theoretically investigate the spectral properties of a quantum impurity (QI) hosting the here proposed Majorana-Ising-type quasiparticle excitation. It arises from the coupling between a finite topological superconductor (TSC) based on a chain of magnetic adatoms-superconducting hybrid system and an integer large spin S flanking the QI. It is noteworthy that the spin S couples to the QI via the Ising-type exchange interaction. As the Majorana zero modes (MZMs) at the edges of the TSC chain are overlapped, we counterintuitively find a regime wherein the Ising term modulates the localization of a fractionalized and resonant MZM at the QI site. Interestingly enough, the fermionic nature of this state is revealed as purely of the electron tunneling type and, most astonishingly, it has the Andreev conductance completely null in its birth. Therefore, we find that a resonant edge state appears as a zero mode and discuss it in terms of a poor man's Majorana [Dvir, Nature 614, 445 (2023)0028-083610.1038/s41586-022-05585-1].ItemArtigo Polaron-assisted electronic transport in ZnP2 nanowires(2023-02-14) de Oliveira, F. M. ; Cabral, L. ; Villegas-Lelovsky, L. ; Lima, Matheus P. ; Aragón, F. F.H. ; Marques, G. E. ; Chiquito, A. J. ; Teodoro, M. D. ; Universidade Federal de São Carlos (UFSCar) ; Universidade Estadual de Campinas (UNICAMP) ; Universidade Estadual Paulista (UNESP) ; Universidad Nacional de San Agustín de ArequipaIn this work, carrier transport in a gold-seeded zinc diphosphide nanowire fabricated by vapor-liquid-solid and photolithography techniques is investigated in detail. The presence of zinc vacancies and interstitial phosphorus along the nanostructure resulted in defect levels evidenced by photoluminescence transitions observed in the near-infrared spectral range (800-900 nm). The electronic transport measurements by thermally stimulated current identified an activation energy of 80 meV, as well as a defect state with photoluminescence emission at 1.40 eV. The electronic transport in the transient regime was verified for temperatures below 50 K up to room temperature, and the photocurrent relaxation was described by a phenomenological model. We observed a well defined square-wave photoresponse of hundreds of nanoamperes per second during 532 nm light excitation, justifying the potential use of the device as a light sensor. Also, for the first time, ab initio calculations were performed considering defects of a Zn monovacancy close to an interstitial P atom to describe the luminescence transitions. The systematic use of a hybrid functional for these defects allows us to determine the presence of polarons due to the distortion of atomic bonds. Through the electronic property simulations, we corroborated the nature of p-type transport in zinc diphosphide nanowires.ItemArtigo Mechanical properties and deformation-driven band gap tuning on [N]-Carbophenes(2023-04-05) Batista, Gabriel H. ; Psofogiannakis, George ; Junkermeier, Chad E. ; Paupitz, Ricardo ; Universidade Estadual Paulista (UNESP) ; University of Ottawa ; University of Hawai‘i Maui College ; University of Hawai‘i at MānoaA new class of two-dimensional carbon-based materials, N-carbophenes, is studied using tight binding density functional theory. The present study addresses the influence of strain on band gap opening for N-Carbophenes where 3 ≤ N ≤ 9. We found that both uniaxial and biaxial strains can lead to significant changes in the electronic structure of N-carbophenes. One unexpected effect was the existence of a maximum value for the band gaps for strains in the range 13%≤ɛ≤15% and that increasing ɛ above that range can cause a reduction in the band gap. The origin of the band gap openings is due to the stretching of C–C bonds in the N-carbophene 4-member rings.ItemArtigo Evidence of progressive Fe2+ to Fe3+oxidation in Fe2+-doped ZnO nanoparticles(2023-02-08) Aragón, F. F.H. ; Villegas-Lelovsky, L. ; Parizaka, J. G. ; Zela, E. G. ; Bendezu, R. ; Gallegos, R. O. ; Pacheco-Salazar, D. G. ; da Silva, S. W. ; Cohen, R. ; Nagamine, L. C.C.M. ; Coaquira, J. A.H. ; Morais, P. C. ; Av Independencia SN ; Institute of Physics ; Universidade Federal de São Carlos (UFSCar) ; Universidade de São Paulo (USP) ; Genomic Sciences and Biotechnology ; Universidade Estadual Paulista (UNESP)Oxide-diluted magnetic semiconductors have received considerable attention in diverse scientific and technological fields because they combine the optoelectronic properties of the hosting semiconductor with the magnetic properties of the metal dopant. In this report, the role of Fe doping on the structural, vibrational, optical, hyperfine, and magnetic properties of Fe-doped ZnO nanoparticles (Zn1−xFexO) synthesized via a polymeric precursor method is presented. Our findings display that the crystallite size decreases from ∼23 nm (x = 0.000) to ∼8 nm (x = 0.200) as the Fe-content (x) is increased. From the XRD data analysis, our results suggest an isovalent solid solution between Fe2+ and Zn2+ ions for lower Fe-content (up to 0.075) and aliovalent solution (Fe3+ and Zn2+ ions) for higher Fe-content. Elliot's theory was used to assess the band gap energy of Eg ∼ 3.4 eV, and an exciton binding energy of Eb ∼ 66 meV for the undoped sample. The excitonic peak exhibits a broadening trend with increasing Fe-content, suggesting disorder enhancement in the ZnO matrix. Besides, FTIR data analysis suggests that the Zn-O bond length increases with Fe-content up to 0.075 and decreases above this value. The intensity ratio of the O-H and Zn-O modes shows a discontinuity as the Fe-content is increased. Room temperature Mössbauer spectra carried out for samples with x = 0.050, 0.075, and 0.200 show that the isomer shift and quadrupole splitting increase with the Fe-content, in agreement with the structural properties. Magnetic measurements suggest that the iron ions stabilize as Fe2+ in samples with low Fe-content and then as Fe3+ in samples with high Fe-content. Besides, the occurrence of short-range antiferromagnetic interactions was determined, which becomes stronger as the Fe-content is increased.ItemArtigo Bifurcations, relaxation time, and critical exponents in a dissipative or conservative Fermi model(2023-02-01) Rando, Danilo S. ; Martí, Arturo C. ; Leonel, Edson D. ; Universidade Estadual Paulista (UNESP) ; Universidad de la RepúblicaWe investigated the time evolution for the stationary state at different bifurcations of a dissipative version of the Fermi-Ulam accelerator model. For local bifurcations, as period-doubling bifurcations, the convergence to the inactive state is made using a homogeneous and generalized function at the bifurcation parameter. It leads to a set of three critical exponents that are universal for such bifurcation. Near bifurcation, an exponential decay describes convergence whose relaxation time is characterized by a power law. For global bifurcation, as noticed for a boundary crisis, where a chaotic transient suddenly replaces a chaotic attractor after a tiny change of control parameters, the survival probability is described by an exponential decay whose transient time is given by a power law.ItemArtigo Synthesis and properties of Cerium-doped organic/silica xerogels: A potential UV filter for photovoltaic panels(2023-01-15) Sandrini, Marcelo ; Gemelli, Jefferson Cristiano ; Gibin, Mariana Sversut ; Zanuto, Vitor Santaella ; Muniz, Robson Ferrari ; de Vicente, Fábio Simões ; Belançon, Marcos Paulo ; Câmpus Pato Branco ; Universidade Estadual de Maringá (UEM) ; Universidade Estadual Paulista (UNESP)The UV-induced polymeric encapsulant degradation in the photovoltaic panel is a challenge in extending the operating lifetime of such devices. To overcome that, an anti-reflective coating material that blocks the UV incidence can be an alternative. In this sense, this work presents high optical quality GPTS/TEOS monolithic xerogels doped with cerium prepared by the sol–gel process. X-ray diffraction, thermal analysis, and infrared spectroscopy results reveal an amorphous hybrid structure stable with the dopant concentration, up to 1 wt%. The undoped matrix shows a wide transmission window, and the cerium addition results in a redshift of the cut-off edge, from ∼300 to 410 nm, and a slight reduction in reflectance. Moreover, all samples present a refractive index well matched with the ethylene-vinyl acetate (EVA) encapsulant, which minimizes reflectance losses. These results highlight the potential of the cerium-doped GPTS/TEOS system as a candidate for UV filter coating on photovoltaic panels.ItemArtigo ZnO-based electrolyte-gated transistor (EGT) applied as multiparametric UV-sensing device(2022-11-01) Vieira, Douglas Henrique ; Nogueira, Gabriel Leonardo ; Morais, Rogério Miranda ; Fugikawa-Santos, Lucas ; Seidel, Keli Fabiana ; Alves, Neri ; Universidade Estadual Paulista (UNESP) ; Physics DepartmentTransistors based in solution-processable semiconducting metal oxides stands out for disposable, printed and wearable electronics. Here we report a transparent and printed ZnO-based electrolyte-gated transistor (EGT), using cellulose electrolyte, which exhibited low-voltage operation, below 2 V, threshold voltage of 0.16 V, high on-state current of 0.3 mA, Ion/Ioff ratio of 3.0 × 105 and field-effect mobility of 0.17 cm²/Vs. We have demonstrated that such EGT can be applied as an ultraviolet sensing device, showing multiparametric response with shift in its: threshold voltage (VT), subthreshold swing (S), transconductance (gm) and enhancement in the field-effect mobility in saturation regime (μs) when exposed to different UV irradiance levels. This device achieves high IUV/Idark ratio, responsivity and EQE of 1 × 105, 8.4 × 104 A/W and 2.7 × 106%, respectively, presenting very stable properties when tested in ambient atmosphere, without encapsulation, and with no visible effects of ageing during the period of observation. The variation in the transistor parameters and the high values of the figures of merit for photodetectors, categorize this EGT as a multiparametric UV sensor with good performance and compatible with printed and transparent electronics.ItemArtigo Multiple Reflections for Classical Particles Moving under the Influence of a Time-Dependent Potential Well(2022-10-01) Graciano, Flávio Heleno ; da Costa, Diogo Ricardo ; Leonel, Edson D. ; de Oliveira, Juliano A. ; Universidade Estadual Paulista (UNESP) ; Instituto Federal do Sul de Minas Gerais (IFSULDEMINAS) ; Universidade Federal do Paraná (UFPR) ; Universidade de São Paulo (USP)We study the dynamics of classical particles confined in a time-dependent potential well. The dynamics of each particle is described by a two-dimensional nonlinear discrete mapping for the variables energy (Formula presented.) and phase (Formula presented.) of the periodic moving well. We obtain the phase space and show that it contains periodic islands, chaotic sea, and invariant spanning curves. We find the elliptic and hyperbolic fixed points and discuss a numerical method to obtain them. We study the dispersion of the initial conditions after a single iteration. This study allows finding regions where multiple reflections occur. Multiple reflections happen when a particle does not have enough energy to exit the potential well and is trapped inside it, suffering several reflections until it has enough energy to exit. We also show deformations in regions with multiple reflection, but the area remains constant when we change the control parameter (Formula presented.). Finally, we show some structures that appear in the (Formula presented.) plane by using density plots.ItemArtigo Circulating levels of vascular endothelial growth factor in patients with Alzheimer's disease: A case-control study(2023-02-02) Silva, Thays Martins Vital da ; Stein, Angelica Miki ; Coelho, Flávia Gomes de Melo ; Rueda, Andre Veloso ; Camarini, Rosana ; Galduróz, Ruth Ferreira ; Instituto Federal do Triangulo Mineiro ; Universidade Estadual Paulista (UNESP) ; Federal University of Technology – Paraná (UTFPR) ; Midwestern Parana State University (UNICENTRO) ; Universidade de São Paulo (USP) ; Universidade Federal do ABC (UFABC)Background: Vascular endothelial growth factor (VEGF) and platelets seem to reflect the Alzheimer's disease (AD) associated either with vascular impairment or disease. This study aimed to compare the circulating levels of VEGF and platelets between AD patients and healthy older adults. Methods: Seventy-two older adults, divided in 40 older adults (Clinical Dementia Rating Scale – CDR = 0); and 32 Alzheimer's disease patients (clinically diagnosed – CRD = 1) participated in the present study. The groups were paired by sex, age, comorbidities and educational level. The primary outcomes included circulating plasma VEGF and platelet levels obtained by blood collection. Results: The VEGF levels were significantly different between the groups (p = 0.03), with having a large effect size ( η2 =18.15), in which the AD patients presented lower levels compared to healthy older adults. For platelets, the comparison showed a tendency to difference (p = 0.06), with a large effect size (η2 =12.95) between the groups. Conclusion: The VEGF levels and the platelet numbers were reduced in AD patients, suggesting that angiogenic factors could be modified due to AD.ItemArtigo Valence state, lattice incorporation, and resulting magnetic properties of Ni in Zn/Co-based magnetic oxides(Aip Publishing, 2023-01-21) Ney, V. ; Henne, B. ; Souza, M. de ; Jantsch, W. ; Johansen, K. M. ; Wilhelm, F. ; Rogalev, A. ; Ney, A. ; Johannes Kepler Univ Linz ; Univ Oslo ; European Synchrotron Radiat Facil ESRF ; Universidade Estadual Paulista (UNESP)Ni incorporation has been studied in a comprehensive range of Zn/Co-based magnetic oxides to elucidate its valence state and lattice incorporation. The resulting structural and magnetic properties of a range of related types of samples are studied in detail. On the one hand, Ni doping is studied in wurtzite ZnO which is either done by in-diffusion of the Ni into bulk ZnO or by reactive magnetron sputtering for Nidoped thin films of ZnO. The latter is complemented by Ni and Co codoping of ZnO leading to altered magnetic properties which are then dominated by Co. On the other hand, the ZnCo2O4 spinel is codoped with varying amounts of Ni. In the wurtzite oxides, Ni is exclusively found on tetrahedral lattice sites in its formal 2+ oxidation state as deep donor. It behaves as an anisotropic paramagnet, and a limited solubility of Ni below 10% is found. Furthermore, the partial compensation of the antiferromagnetically coupled Co magnetic moments is induced by the Ni due to its smaller magnetic moment. In the ZnCo2O4 spinel, Ni is found to be incorporated in its formal 3+ oxidation state on octahedral sites and also couples antiferromagnetically to the Co moments. At low Ni concentrations, this leads to a lifting of the partial magnetic compensation of the antiferromagnetic ZnCo2O4 spinel and to ferrimagnetism at higher Ni concentrations. Increasing the Ni concentration even further leads to phase separation of cubic NiO resulting in a structurally less defined, exchange-biased composite magnetic oxide.ItemArtigo Tunable Orbits Influence in a Driven Stadium-Like Billiard(Springer, 2019-01-01) Livorati, Andre L. P. ; Macau, EEN ; Universidade Estadual Paulista (UNESP) ; Univ BristolItemArtigo An Investigation of the Chaotic Transient for a Boundary Crisis in the Fermi-Ulam Model(Springer, 2019-01-01) Leonel, Edson D. ; Marques, Murilo F. ; Macau, EEN ; Universidade Estadual Paulista (UNESP)ItemArtigo OBTAINING MAGNETIC AND ELECTRIC INFORMATION ON ORGANIC SYSTEMS USING ELECTRON SPIN RESONANCE(Nova Science Publishers, Inc, 2009-01-01) Walmsey, L. ; Tamayo, K. B. ; Universidade Estadual Paulista (UNESP)A very rich diversity of magnetic ordering can be found in organic systems, and in many of these systems an electron spin resonance (ESR) line can be observed even at room temperature. This fact allows a great deal of information to be obtained for a broad range of temperatures. Among other factors, information can be collected about the surroundings of the magnetic moments, the mechanisms of relaxation of the magnetization, the interaction with other magnetic moments and if they are localized or delocalized. The possibility to compare the ESR magnetic data with data obtained from magnetic measurements using volume techniques like magnetization obtained from Vibrating Sample Magnetometers (VSM) or Superconductor Quantum Interference Device (SQUID) magnetometers, allows a detailed analysis of the magnetic systems under study. In certain special situations, for some particular geometrical conditions, the conductivity at the microwave frequency can also be obtained from the ESR line asymmetry, providing a simple and precise method of contactless conductivity measurements.ItemTrabalho apresentado em evento MULTIPLE ACTIVE LEVELS IN Bi12TiO20 CRYSTALS(2001-01-01) Freschi, A. A. ; Donatti, D. A. ; Frejlich, J. ; Universidade Estadual Paulista (UNESP) ; Universidade Estadual de Campinas (UNICAMP)The existence of multiple active levels in a photorefractive Bi12TiO20 crystal is here investigated at 514.5nm wavelength. We carry out two-wave mixing experiments using symmetrically incident beams of equal intensities. A large amplitude fast phase modulation in one of the beams reduces the fringes visibility and improves the detection of the generated frequency modulated signals in both (R and S) output directions. Diffraction efficiencies of the phase (photorefractive) and the absorption (photochromic) gratings are quantitatively computed as functions of the grating period. Results show that the absorption grating has two distinct components: one associated to the photorefractive trap density modulation and another related to local light-induced effects between different levels. The photorefractive grating was also investigated at 633nm and 594nm (besides 514.5nm) and a significant quenching of the photorefractive effect was observed at these wavelengths.ItemArtigo Break-up of invariant curves in the Fermi-Ulam model(2022-09-01) Hermes, Joelson D.V. ; dos Reis, Marcelo A. ; Caldas, Iberê L. ; Leonel, Edson D. ; Science and Technology of South of Minas Gerais - IFSULDEMINAS ; Universidade Estadual Paulista (UNESP) ; Campinas ; Universidade de São Paulo (USP)The transport of particles in the phase space is investigated in the Fermi-Ulam model. The system consists of a particle confined to move within two rigid walls with which it collides. One is fixed and the other is periodically moving in time. In this work we investigate, for this model, the location of invariant curves that separate chaotic areas in the phase space. Applying the Slater's theorem we verify that the mapping presents a family of invariant spanning curves with a rotation number whose expansion into continued fractions has an infinite tail of the unity, acting as local transport barriers. We study the destruction of such curves and find the critical parameters for that. The determination of the rotation number in the vicinity of one of the considered spanning curves allowed us to understand the dynamics in the vicinity of the considered curve, both before and after criticality. The rotation number profile showed us the fractal character of the region close to the curve, since this profile has a structure similar to a “Devil's Staircase”.ItemArtigo Topological charge Fano effect in multi-Weyl semimetals(2022-06-15) Silva, W. C. ; Mizobata, W. N. ; Sanches, J. E. ; Ricco, L. S. ; Shelykh, I. A. ; De Souza, M. ; Figueira, M. S. ; Vernek, E. ; Seridonio, A. C. ; Universidade Estadual Paulista (UNESP) ; University of Iceland ; Itmo University ; Universidade Federal Fluminense (UFF) ; Universidade Federal de Uberlândia (UFU)We theoretically analyze the Fano interference in a single impurity multi-Weyl semimetal hybrid system and show the emergence of the topological charge Fano effect in the bulk local density of states. In multi-Weyl semimetals, the number of Fermi arcs at the system boundaries is determined by the topological charge J, a direct consequence of the bulk-boundarycorrespondence principle. Analogously, we find that J also modulates the bulk Fano profile of the system with an embedded quantum impurity. Thus by increasing J, the Fano line shape evolves from resonant, typical for J=1 (single Weyl), towards antiresonant, extrapolating to the so-called hyper Weyl semimetals with J≫1. Specially for the maximum case protected by the rotational symmetry C2J=6, namely, the J=3 (triple Weyl), which acquires asymmetric Fano profile, the Fano parameter absolute value is predicted to be tan(C2J=6), where C2J(360∘/2J) defines the rotational angle. Hence, the Fano discretization in the J term introduces the topological charge Fano effect in multi-Weyl semimetals. We also suggest a transport device where we expect that the proposed Fano effect could be detected.ItemArtigo Tuning intrinsic defects in ZnO films by controlling the vacuum annealing temperature: An experimental and theoretical approach(2022-07-01) Paz-Corrales, K. J. ; Vilca-Huayhua, C. A. ; Aragón, F. F.H. ; Villegas-Lelovsky, L. ; Coaquira, J. A.H. ; Da Silva, S. W. ; Marques, G. E. ; Teodoro, M. D. ; Pacheco-Salazar, D. G. ; Universidad Nacional de San Agustín de Arequipa ; Universidade de Brasília (UnB) ; Universidade Estadual Paulista (UNESP) ; Universidade Federal de São Carlos (UFSCar)The control of native defects in the ZnO material is strongly important for a wide range of technological applications. In this paper, native defects are tuned via the post-thermal treatment of ZnO films in a high vacuum atmosphere. The microstructure of the as-grown ZnO film shows columnar growth and strongly polar-oriented grains along the c-plane (002). Also, the obtained results indicate that the as-grown film contains a high amount of intrinsic defects and strong lattice distortions. After the thermal annealing, the ZnO films display significant structural changes, which are reflected in their electrical, vibrational, and optical properties. Our findings suggest that these changes were attributed to the selective cleanup effect of the native defects and the partial deoxidation process mainly on the exposed particle surface (at high temperatures) tuned up by the thermal annealing temperature. According to DFT calculations, oxygen vacancies (V O ) show lower energy, followed by zinc vacancies (V Zn ) and oxygen interstitials (O i ) indicating that V O defect is the most stable in ZnO. That sequence of stability could suggest the sequence of the annihilation of those defects, which is in line with our experimental findings and also in agreement with literature results.ItemArtigo Basin sizes depend on stable eigenvalues in the Kuramoto model(2022-05-01) Mihara, Antonio ; Zaks, Michael ; Macau, Elbert E. N. ; Medrano-T, Rene O. ; Universidade Federal de São Paulo (UNIFESP) ; Humboldt University of Berlin ; Universidade Estadual Paulista (UNESP)We show that for the Kuramoto model (with identical phase oscillators equally coupled), its global statistics and size of the basins of attraction can be estimated through the eigenvalues of all stable (frequency) synchronized states. This result is somehow unexpected since, by doing that, one could just use a local analysis to obtain the global dynamic properties. But recent works based on Koopman and Perron-Frobenius operators demonstrate that the global features of a nonlinear dynamical system, with some specific conditions, are somehow encoded in the local eigenvalues of its equilibrium states. Recognized numerical simulations in the literature reinforce our analytical results.ItemArtigo Bi-chromaticity and tunability of random lasing in mesoporous silica SBA16 doped with rhodamine B(2022-07-01) Melo, Leandro A. ; Prado, Marcus V. A. ; Vicente, Fábio S. de ; Moreno, Leandro X. ; Rodrigues Jr, José Joatan ; Alencar, Márcio A. R. C. ; Universidade Federal de Sergipe (UFS) ; Universidade Estadual Paulista (UNESP)The random laser emission from ordered mesoporous silica SBA16 doped with rhodamine B (RB) organic dye was investigated. Powdered SBA16 with 16 nm average pore diameter have been synthesized and doped with five different concentrations of the organic dye. Typical incoherent feedback random laser behavior was observed. The bi-chromatic emission was characterized for the sample with the highest dye concentration. Tunable random laser emissions from 578 to 618 nm were obtained depending on the excitation laser spot diameter and the rhodamine-B load. The results indicate that mesoporous RB-doped SBA16 is a promising material for the development of solid-state random lasers.