Catálogo de publicaciones - revistas

<jats:p> <jats:italic>In recent years, orbital angular momentum (OAM), as a new usable degree of freedom of photons, has been widely applied in both classical optics and quantum optics. For example, digital spiral imaging uses the OAM spectrum of the output beam from the object to restore the symmetry information of the object. However, the related experiments have been carried out in free space so far. Due to the poor anti-noise performance, limited transmission distance and other reasons, the practicability is seriously restricted. Here, we have carried out a digital spiral imaging experiment through a few-mode fiber, to achieve the identification of the symmetry of object by measuring the OAM spectrum of the output beam. In experiment, we have demonstrated the identification of the symmetry of amplitude-only and phase-only objects with the two-, three- and four-fold rotational symmetries. We also give the understanding of the physics. We believe that our work has greatly improved the practical application of digital spiral imaging in remote sensing</jats:italic>.</jats:p>

<jats:p> <jats:italic>Using the linear local induction approximation, we investigate the self-induced motion of a vortex-line that corresponds to the motion of a particle in quantum mechanics. Provided Kelvin waves, the effective Schrödinger equation, physical quantity operators, and the corresponding path-integral formula can be obtained. In particular, the effective Planck constant defined by parameters of vortex-line motion shows the mathematical relation between the two fields. The vortexline–particle mapping may help in understanding particle motion in quantum mechanics</jats:italic>.</jats:p>

<jats:p>An ultra-thin molybdenum(VI) oxide (MoO<jats:sub>3</jats:sub>) modification layer can significantly improve hole injection from an electrode even though the MoO<jats:sub>3</jats:sub> layer does not contact the electrode. We find that as the thickness of the organic layer between MoO<jats:sub>3</jats:sub> and the electrode increases, the hole injection first increases and it then decreases. The optimum thickness of 5 nm corresponds to the best current improvement 70%, higher than that in the device where MoO<jats:sub>3</jats:sub> directly contacts the Al electrode. According to the 4,4-bis[N-(1-naphthyl)-N-phenyl-amino] biphenyl (NPB)/MoO<jats:sub>3</jats:sub> interface charge transfer mechanism and the present experimental results, we propose a mechanism that mobile carriers generated at the interface and accumulated inside the device change the distribution of electric field inside the device, resulting in an increase of the probability of hole tunneling through the injection barrier from the electrode, which also explains the phenomenon of hole injection enhanced by MoO<jats:sub>3</jats:sub>/NPB/Al composite anode. Based on this mechanism, different organic materials other than NPB were applied to form the composite electrode with MoO<jats:sub>3</jats:sub>. Similar current enhancement effects are also observed.</jats:p>

<jats:p>We report a <jats:sup>19</jats:sup>F nuclear magnetic resonance (NMR) study on single-crystal KCa<jats:sub>2</jats:sub>Fe<jats:sub>4</jats:sub>As<jats:sub>4</jats:sub>F<jats:sub>2</jats:sub> (<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> ∼ 33.3 K). The <jats:sup>19</jats:sup>F NMR spectral shape of KCa<jats:sub>2</jats:sub>Fe<jats:sub>4</jats:sub>As<jats:sub>4</jats:sub>F<jats:sub>2</jats:sub> is weakly dependent on temperature and the Knight shift is small, which implies weak coupling between the CaF layer and the FeAs layer. The temperature dependence of 1/<jats:sup>19</jats:sup> <jats:italic>T</jats:italic> <jats:sub>1</jats:sub> shows a hump below <jats:italic>T</jats:italic> <jats:sub>c</jats:sub>, however the 1/<jats:sup>75</jats:sup> <jats:italic>T</jats:italic> <jats:sub>1</jats:sub> decreases just below <jats:italic>T</jats:italic> <jats:sub>c</jats:sub>, which implies that there are strong in-plane magnetic fluctuations in the CaF layers than in the FeAs layers. This may be caused by the motion of vortices. The absence of the coherence peak suggests unconventional superconductivity in KCa<jats:sub>2</jats:sub>Fe<jats:sub>4</jats:sub>As<jats:sub>4</jats:sub>F<jats:sub>2</jats:sub>.</jats:p>

<jats:p>We propose a diamond-based micron-scale sensor and perform high-resolution <jats:italic>B</jats:italic>-field imaging of the near-field distribution of coplanar waveguides. The sensor consists of diamond crystals attached to the tip of a tapered fiber with a physical size on the order of submicron. The amplitude of the <jats:italic>B</jats:italic>-field component <jats:italic>B</jats:italic> is obtained by measuring the Rabi oscillation frequency. The result of Rabi sequence is fitted with a decayed sinusoidal. We apply the modulation-locking technique that demonstrates the vector-resolved field mapping of the micromachine coplanar waveguide structure (CPW). <jats:italic>B</jats:italic>-field line scan was performed on the CPW with a scan step size of 1.25 μm. To demonstrate vector resolved rf field sensing, a full field line scan acts (was performed) along four NV axes at a height of 50 μm above the device surface. The simulations are compared with the experimental results by vector-resolved measurement. This technique allows the measurement of weak microwave signals with a minimum resolvable modulation depth of 20 ppm. The sensor will have great interest in micron-scale resolved microwave <jats:italic>B</jats:italic>-field measurements, such as electromagnetic compatibility testing of microwave integrated circuits and characterization of integrated microwave components.</jats:p>

<jats:p>We investigate the evolution of entanglement spectra under a global quantum quench from a short-range correlated state to the quantum critical point. Motivated by the conformal mapping, we find that the dynamical entanglement spectra demonstrate distinct finite-size scaling behaviors from the static case. As a prototypical example, we compute real-time dynamics of the entanglement spectra of a one-dimensional transverse-field Ising chain. Numerical simulation confirms that the entanglement spectra scale with the subsystem size <jats:italic>l</jats:italic> as ∼<jats:italic>l</jats:italic> <jats:sup>−1</jats:sup> for the dynamical equilibrium state, much faster than ∝ ln<jats:sup>−1</jats:sup> <jats:italic>l</jats:italic> for the critical ground state. In particular, as a byproduct, the entanglement spectra at the long time limit faithfully gives universal tower structure of underlying Ising criticality, which shows the emergence of operator-state correspondence in the quantum dynamics.</jats:p>

<jats:p>It is very important to increase the quantum efficiency (QE) and prolong the lifetime of the photocathode in a variety of applications. We have succeeded in preparing a high QE cesium potassium antimonide (K–Cs–Sb) photocathode by K and Cs co-evaporation in the photocathode preparation facility. In order to better understand the effect of the substrate (photocathode) temperature on the photocathode performance, the photocathode preparation, photocathode performance degradation, photocathode performance recovery and photocathode removal are studied in detail.</jats:p>

<jats:p>In the band structure of graphene, the dispersion relation is linear around a Dirac point at the corners of the Brillouin zone. The closed graphene system has proven to be the ideal model to investigate relativistic quantum chaos phenomena. The electromagnetic material photonic graphene (PG) and electronic graphene not only have the same structural symmetry, but also have the similar band structure. Thus, we consider a stadium shaped resonant cavity filled with PG to demonstrate the relativistic quantum chaos phenomenon by numerical simulation. It is interesting that the relativistic quantum scars not only are identified in the PG cavities, but also appear and disappear repeatedly. The wave vector difference between repetitive scars on the same orbit is analyzed and confirmed to follow the quantization rule. The exploration will not only demonstrate a visual simulation of relativistic quantum scars but also propose a physical system for observing valley-dependent relativistic quantum scars, which is helpful for further understanding of quantum chaos.</jats:p>

<jats:p>We realize a coherent transfer of mechanical excitation in a finely controlled artificial nanomechanical lattice. We also realize strong dynamic coupling between adjacent high-<jats:italic>Q</jats:italic> mechanical resonators, via modulated dielectric force at the frequency difference between them. An excitation transfer across a lattice consisting of 7 nanobeams is observed by applying a design sequence of switching for couplings, with the final effective population reaching 0.94. This work not only demonstrates the ability to fully control an artificial lattice but also provides an efficient platform for studying complicated dynamics in one-dimensional systems.</jats:p>

<jats:p>A new model of two-phase thermocapillary-buoyancy convection with phase change at gas-liquid interface in an enclosed cavity subjected to a horizontal temperature gradient is proposed, rather than the previous one-sided model without phase change. We study the onset of multicellular convection and two modes of convective instability, and find four different flow regimes. Their transition map is compared with the non-phase-change condition. Our numerical results show the stabilizing effect of interfacial phase change on the thermocapillary-buoyancy convection.</jats:p>