Catálogo de publicaciones - revistas

<jats:p>Superconductivity and its relationship with strain remains elusive in the monolayer FeSe superconductor. Based on first-principles calculations and model studies, we investigate the magnetic properties of FeSe and FeTe monolayers and find that tensile strain induces changes to magnetic phases for both materials. Furthermore, we reveal that electron doping will decrease the difference of effective magnetic interactions between the <jats:italic>a</jats:italic> and <jats:italic>b</jats:italic> directions in an FeSe monolayer and hence suppress its nematicity. We suggest that the overall effect of tensile strain combined with electron doping hinders the appearance of both magnetic and nematic orders in an FeSe monolayer, which paves the way for the emergence of superconductivity.</jats:p>

<jats:p>The effect of temperature on the characteristics of gallium nitride (GaN) Schottky barrier diodes (SBDs) with TiN and Ni anodes is evaluated. With increasing the temperature from 25 to 175°C, reduction of the turn-on voltage and increase of the leakage current are observed for both GaN SBDs with TiN and Ni anodes. The performance after thermal treatment shows much better stability for SBDs with TiN anode, while those with Ni anode change due to more interface states. It is found that the leakage currents of the GaN SBDs with TiN anode are in accord with the thermionic emission model whereas those of the GaN SBDs with Ni anode are much higher than the model. The Silvaco TCAD simulation results show that phonon-assisted tunneling caused by interface states may lead to the instability of electrical properties after thermal treatment, which dominates the leakage currents for GaN SBDs with Ni anode. Compared with GaN SBDs with Ni anode, GaN SBDs with TiN anode are beneficial to the application in microwave power rectification fields due to lower turn-on voltage and better thermal stability.</jats:p>

<jats:p>We report a systematic study on magnetotransport properties of the single crystal of cadmium (Cd). When the applied magnetic field <jats:italic>B</jats:italic> is perpendicular to the current <jats:italic>I</jats:italic>, the resistivities for both directions (<jats:italic>I</jats:italic> || <jats:italic>a</jats:italic>, <jats:italic>I</jats:italic> || <jats:italic>c</jats:italic>) show field induced metal-to-insulator-like transitions. The isothermal magnetoresistance (MR) at low temperatures increases approximately as the square of the magnetic field without any sign of saturation, and reaches up to 1140000% and 58000% at <jats:italic>T</jats:italic> = 2 K and <jats:italic>B</jats:italic> = 9 T for <jats:italic>I</jats:italic> || <jats:italic>a</jats:italic> and <jats:italic>I</jats:italic> || <jats:italic>c</jats:italic>, respectively. As the magnetic field rotates to parallel to the current, no sign of negative MR is observed for <jats:italic>I</jats:italic> || <jats:italic>a</jats:italic>, while an obvious negative MR appears up to −70% at 2 K and 9 T for the current flowing along the <jats:italic>c</jats:italic>-axis, and the negative longitudinal MR shows a strong dependence of the electrode position on the single crystal. These results suggest that the negative longitudinal MR is caused by the dislocations formed in the process of crystal growing along the <jats:italic>c</jats:italic>-axis. Further studies are needed to clarify this point.</jats:p>

<jats:p> <jats:italic>Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative (PIN) structures on silicon wafer by a gas source molecule beam epitaxy system and the investigate the absorption coefficient through the photovoltaic processes in detail. It is found that the absorption coefficient is enhanced by one order and can be tuned greatly through the thickness of the intrinsic layer in the PIN structure, which is also demonstrated by the 730-nm-wavelength laser irradiation. These results cannot be explained by the traditional absorption theory. We speculate that there could be some uncovered mechanism in this system, which will inspire us to understand the absorption process further.</jats:italic> </jats:p>

<jats:p> <jats:italic>A double-tapered AlGaN electron blocking layer (EBL) is proposed to apply in a deep ultraviolet semiconductor laser diode. Compared with the inverse double-tapered EBL, the laser with the double-tapered EBL shows a higher slope efficiency, which indicates that effective enhancement in the transportation of electrons and holes is achieved. Particularly, comparisons among the double-tapered EBL, the inverse double-tapered EBL, the single-tapered EBL and the inverse single-tapered EBL show that the double-tapered EBL has the best performance in terms of current leakage.</jats:italic> </jats:p>

<jats:p> <jats:italic>We demonstrate theoretically the anisotropic quantum transport of electrons through an electric field on monolayer and multilayer phosphorene. Using the long-wavelength Hamiltonian with continuum approximation, we find that the transmission probability for transport through an electric field is an oscillating function of incident angle, electric field intensity, as well as the incident energy of electrons. By tuning the electric field intensity and incident angle, the channels can be transited from opaque to transparent. The conductance through the quantum waveguides depends sensitively on the transport direction because of the anisotropic effective mass, and the anisotropy of the conductance can be tuned by the electric field intensity and the number of layers. These behaviors provide us an efficient way to control the transport of phosphorene-based microstructures.</jats:italic> </jats:p>

<jats:p> <jats:italic>A kind of n-type HoF<jats:sub>3</jats:sub>-doped zinc oxide-based transparent conductive film has been developed by electron beam evaporation and studied under thermal annealing in air and vacuum at temperatures 100–500°C. Effective substitutional dopings of F to O and Ho to Zn are realized for the films with smooth surface morphology and average grain size of about 50 nm. The hall mobility, electron concentration, resistivity and work function for the as-deposited films are 47.89 cm<jats:sup>2</jats:sup>/Vs, 1.39×10<jats:sup>20</jats:sup> cm<jats:sup>−3</jats:sup>, 9.37 × 10<jats:sup>−4</jats:sup> Ω·cm and 5.069 eV, respectively. In addition, the average transmittance in the visible region (400–700 nm) approximates to 87%. The HoF<jats:sub>3</jats:sub>:ZnO films annealed in air and vacuum can retain good optoelectronic properties under 300°C, thereinto, more stable electrical properties can be found in the air-annealed films than in the vacuum-annealed films, which is assumed to be a result of improved nano-crystalline lattice quality. The optimized films for most parameters can be obtained at 200°C for the air-annealing case and at room temperature for the vacuum annealing case. The advisable optoelectronic properties imply that HoF<jats:sub>3</jats:sub>:ZnO can facilitate carrier injection and has promising applications in energy and light sources as transparent electrodes.</jats:italic> </jats:p>

<jats:p>TlBa<jats:sub>2</jats:sub>Ca<jats:sub>2</jats:sub>Cu<jats:sub>3</jats:sub>O<jats:sub>9</jats:sub> (Tl-1223) films have promising applications due to their high critical temperature and strong magnetic flux pinning. Nevertheless, the preparation of pure phase Tl-1223 film is still a challenge. We successfully fabricate Tl-1223 thin films on LaAlO<jats:sub>3</jats:sub> (001) substrates using dc magnetic sputtering and a post annealing two-step method in argon atmosphere. The crystallization temperature of Tl-1223 films in argon is reduced by 100°C compared to that in oxygen. This greatly reduces the volatilization of Tl and improves the surface morphology of films. The lower annealing temperature can effectively improve the repeatability of the Tl-1223 film preparation. In addition, pure Tl-1223 phase can be obtained in a broad temperature zone, from 790°C to 830°C. In our study, the films show homogenous and dense surface morphology using the presented method. The best critical temperature of Tl-1223 films is characterized to be 110 K, and the critical current <jats:italic>J</jats:italic> <jats:sub>c</jats:sub> (77 K, 0 T) is up to 2.13 × 10<jats:sup>6</jats:sup> A/cm<jats:sup>2</jats:sup>.</jats:p>

<jats:p> <jats:italic>We present low-temperature magnetization, magnetoresistance and specific heat measurements on the Kondo lattice compound CePt<jats:sub>3</jats:sub>P under applied magnetic fields up to 9.0 T. At zero field, CePt<jats:sub>3</jats:sub>P exhibits a moderately enhanced Sommerfeld coefficient of electronic specific heat <jats:italic>γ</jats:italic> <jats:sub>Ce</jats:sub> = 86 mJ/mol·K<jats:sup>2</jats:sup> as well as two successive magnetic transitions of Ce 4<jats:italic>f</jats:italic> moments: an antiferromagnetic ordering at <jats:italic>T</jats:italic> <jats:sub>N1</jats:sub> = 3.0K and a spin reorientation at <jats:italic>T</jats:italic> <jats:sub>N2</jats:sub> = 1.9 K. The value of <jats:italic>T</jats:italic> <jats:sub>N1</jats:sub> shifts to lower temperature as magnetic field increases, and it is ultimately suppressed around <jats:italic>B</jats:italic> <jats:sub>c</jats:sub> ∼ 3.0T at 1.5 K. No evidence of non-Fermi liquid behavior is observed around <jats:italic>B</jats:italic> <jats:sub>c</jats:sub> down to the lowest temperature measured. Moreover, <jats:italic>γ</jats:italic> decreases monotonously with increasing the magnetic field. On the other hand, the electrical resistivity shows an anomalous temperature dependence <jats:italic>ρ</jats:italic> ∝ <jats:italic>T</jats:italic> <jats:sup> <jats:italic>n</jats:italic> </jats:sup> with the exponent <jats:italic>n</jats:italic> decreasing monotonously from ∼2.6 around <jats:italic>B</jats:italic> <jats:sub>c</jats:sub> down to ∼1.7 for <jats:italic>B</jats:italic> = 9.0 T. The <jats:italic>T</jats:italic>–<jats:italic>B</jats:italic> phase diagram constructed from the present experimental results of CePt<jats:sub>3</jats:sub>P does not match the quantum criticality scenario of heavy fermion systems.</jats:italic> </jats:p>

<jats:p> <jats:italic>With the development of quantum information processing, multipartite entanglement measures are needed in many cases. However, there are still no complete orthogonal genuine multipartite entanglement (GME) bases available as Bell states to bipartite systems. To achieve this goal, we find a method to construct complete orthogonal GME states, and we exclude many equivalent states by leveraging the group theory. We also provide the case of a 3-order 3-dimensional Hilbert space as an example and study the application of general results in the dense coding scheme as an application. Moreover, we discuss some open questions and believe that this work will enlighten extensive studies in this field.</jats:italic> </jats:p>