Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Carbon nanotubes (CNTs) have attracted many researcher’s attention in gas sensing field because of their excellent physical and chemical properties. Herein, Multi-walled carbon nanotubes (MWCNTs)/ZnSnO<jats:sub>3</jats:sub> heterostructures have been obtained by a simple hydrothermal method without additional annealing process. The structural and composition information are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The acetone sensing properties of pure MWCNTs, ZnSnO<jats:sub>3</jats:sub> and MWCNTs/ZnSnO<jats:sub>3</jats:sub> heterostructures are systematically investigated, respectively. The results show that MWCNTs/ZnSnO<jats:sub>3</jats:sub> heterostructures have better sensing properties compared with pure MWCNTs and ZnSnO<jats:sub>3</jats:sub> sample. Specifically, MWCNTs/ZnSnO<jats:sub>3</jats:sub> heterostructures exhibit not only high responses of 24.1 and rapid response/recovery speed of 1 s/9 s to 100 ppm acetone, but also relatively good repeatability and long-term stability. The enhanced sensing performance is analyzed in detail. In addition, this work provides the experimental and theory basis for synthesis of high-performance MWCNT-based chemical sensors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, an aluminum (Al) based nearly guided-wave surface plasmon resonance (NGWSPR) sensor is investigated in the far-ultraviolet (FUV) region. By simultaneously optimizing the thickness of Al and dielectric films, the sensitivity of the optimized Al-based FUV-NGWSPR sensor increases from 183 to 309°/RIU, and its figure of merit rises from 26.47 to 32.59/RIU when the refractive index of dielectric increases from 2 to 5. Compared with a traditional FUV-SPR sensor without dielectric, the optimized FUV-NGWSPR sensor can realize simultaneous improvement of sensitivity and figure of merit. In addition, the FUV-NGWSPR sensor with realistic materials (diamond, Ta<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub> and GaN) is also investigated, and 137.84%, 52.70% and 41.89% sensitivity improvement are achieved respectively. This work proposes a method for performance improvement of FUV-SPR sensors by exciting nearly guided-wave, and could be helpful for the high-performance SPR sensor in the short-wavelength region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex-vortex interactions, including the competing one in the recently proposed type-1.5 superconductor. However, potential candidate that can be used to study the multicomponent superconductivity is rare. Here, we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent superconductivity. The additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting layer. The magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic superconductivity. The vortex phase diagram and the optimum critical current density have been determined. Furthermore, a second magnetization effect is observed, and is attributed to the upper layer, which provides the weak pinning sites to localize the flux lines. The pinning behaviors switches to the mixed type with the increase of the insulting layer thicknesses. Our results open a new perspective to the study and related applications of the multilayer superconducting systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The original variational quantum eigensolver (VQE) typically minimizes energy with hybrid quantum-classical optimization that aims to find the ground state. Here, we propose VQE based on minimizing energy variance and call it variance-VQE (VVQE), which treats the ground state and excited states on the same footing, since an arbitrary eigenstate for a Hamiltonian should have zero energy variance. We demonstrate the properties of VVQE for solving a set of excited states in quantum chemistry problems. Remarkably, we show that optimization of a combination of energy and variance may be more efficient to find low-energy excited states than those of minimizing energy or variance alone. We further reveal that the optimization can be boosted with stochastic gradient descent by Hamiltonian sampling, which uses only a few terms of the Hamiltonian and thus significantly reduces the quantum resource for evaluating variance and its gradients.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The solar-blind ultraviolet(UV) photodetectors(PDs) with metal-semiconductor-metal(MSM) structure were fabricated based on β-(Al<jats:sub>0.25</jats:sub>Ga<jats:sub>0.75</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/β-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> film grown by metal-organic chemical vapor deposition(MOCVD).And yet,various surface states increase dark current and a large number of defects can hinder the transport of carriers, resulting in low switching ratio and low responsivity of the device. In this paper,β-(Al<jats:sub>0.25</jats:sub>Ga<jats:sub>0.75</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films are used as surface passivation materials, in addition owning to its wide band gap, excellent light transmission and high lattice matching with β-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>. We explored the change and mechanism of the detection performance of the β-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> detector after β-(Al<jats:sub>0.25</jats:sub>Ga<jats:sub>0.75</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> surface passivation. It was found that under the illumination with 254 nm light at 5 V bias, the β-(Al<jats:sub>0.25</jats:sub>Ga<jats:sub>0.75</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/β-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> PDs showed dark current is just 18 pA and high current on/off ratio is 2.16× 10<jats:sup>5</jats:sup>,the dark current is sharply reduced about 50 times after passivation of the β-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> surface, and current on/off ratio increased by approximately 2 times.The results show that β-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> detectors with β-(Al<jats:sub>0.25</jats:sub>Ga<jats:sub>0.75</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> surface passivation offer superior detector performance.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the structure of the continuous matrix product operator (cMPO) [1] for the transverse field Ising model (TFIM). We prove TFIM's cMPO is solvable and has the form $T=e^{-\frac{1}{2}\hat{H}_F}$. $\hat{H}_F$ is a non-local free fermionic hamiltonian on a ring with circumference $\beta$, whose ground state is gapped and non-degenerate even at the critical point. The full spectrum of $\hat{H}_F$ is determined analytically. At the critical point, our results verify the state-operator-correspondence [2] in the conformal field theory (CFT). We also design a numerical algorithm based on Bloch state ansatz to calculate the low-lying excited states of general (hermitian) cMPO. Our numerical calculations coincide with the analytic results of TFIM. In the end, we give a short discussion about the entanglement entropy of cMPO's ground state.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the dynamics of the quantum steering between two separated qubits trapped in a one-dimensional plasmonic waveguide. By numerical methods, we calculate the quantum steerability and other quantum correlations, i.e., entanglement, discord, and coherence, for both cases with and without laser driving fields. It is found that steerability may exhibit a sudden disappearance and sudden reappearance phenomenon. Specifically, there exist time windows with no steerability but finite entanglement. The effects of plasmon wave number and the distance between the two qubits on steerability are also examined. Furthermore, we show that quantum steerability is tunable by adjusting the laser driving fields.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ultrathin superconducting Nb films of about 8 nm thick have been deposited on heavily doped Si substrates through DC magnetron sputtering and then the high-quality Nb/Si superconductor-semiconductor heterojunctions have been fabricated by electron beam lithography and reactive ion etching technology. An abnormal magnetoresistance effect, which manifests as a zero field resistance peak under the magnetic field applied perpendicular to the heterojunction interface, has been distinctly observed when the Nb film is in the superconducting state. By considering the heterojunction interface being equivalent to the structure of superconductor-barrier layer-superconductor configuration, we could generally understand this unusual effect based on the Andreev reflection microscopic mechanism. In addition to the significant value in fundamental research, our results can be of some help for the future development on compatibility and scalability of the silicon-based nanoscale superconducting devices for integrated circuits and superconducting quantum electronics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnonics is a fascinating and emerging field, which mainly studies processing information with spin waves. Magnonic devices with in-plane magnetization have recently been realized. Because of the isotropic propagation, magnonic devices based on perpendicular magnetization are attracting extensive interesting. Here, we numerically demonstrate two magnonic filters with out-of-plane magnetization by micromagnetic simulations. The band-pass and the band-stop functions have been realized in two structurally modulated waveguides, respectively. The intensity of spin waves is manipulated when they arrive at the uniformly/non-uniformly magnetized modulators, which result in the variation of transmission coefficients. It is found that the proposed filters can work at multiple frequencies, which can be further adjusted by the external magnetic field. Our results of designing magnonic devices with Néel-type skyrmion could promote the development of spin wave computing using spin textures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A four-stage cascaded variable optical attenuator (VOA) with a large attenuation range is presented. The VOA is based on Mach-Zehnder Interferometer (MZI) and fabricated in the silica-based planar lightwave circuit (PLC) platform. The thermo-optic effect is used to achieve intensity modulation. The measured maximum attenuation of the four-stage cascaded VOA is 88.38 dB. The chip is also tested in a quantum key distribution (QKD) system to generate signal state and decoy states. The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1, which can meet the requirement of QKD.</jats:p>