Catálogo de publicaciones - revistas

<jats:p>FeSO<jats:sub>4</jats:sub> has the characteristics of low cost and theoretical high energy density (799 W⋅h⋅kg<jats:sup>−1</jats:sup> with a two-electron reaction), which can meet the demand for next-generation lithium-ion batteries. Herein, FeSO<jats:sub>4</jats:sub> as a novel high-performance conversion-reaction type cathode is investigated. We use dopamine as a carbon coating source to increase its electronic conductivity. FeSO<jats:sub>4</jats:sub>@C demonstrates a high reversible specific capacity (512 mA⋅h⋅g<jats:sup>−1</jats:sup>) and a superior cycling performance (482 mA⋅h⋅g<jats:sup>−1</jats:sup> after 250 cycles). In addition, we further study its reaction mechanism. The FeSO<jats:sub>4</jats:sub> is converted to Fe and Li<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub> during lithium ion insertion and the Fe|Li<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub> grain boundaries further store additional lithium ions. Our findings are valuable in exploring other new conversion-type lithium ion battery cathodes.</jats:p>

<jats:p>Interfacial structure evolution and degradation are critical to the electrochemical performance of LiCoO<jats:sub>2</jats:sub> (LCO), the most widely studied and used cathode material in lithium ion batteries. To understand such processes requires precise and quantitative measurements. Herein, we use well-defined epitaxial LCO thin films to reveal the interfacial degradation mechanisms. Through our systematical investigations, we find that surface corrosion is significant after forming the surface phase transition layer, and the cathode electrolyte interphase (CEI) has a double layer structure, an inorganic inner layer containing CoO, LiF, LiOH/Li<jats:sub>2</jats:sub>O and Li<jats:sub> <jats:italic>x</jats:italic> </jats:sub>PF<jats:sub> <jats:italic>y</jats:italic> </jats:sub>O<jats:sub> <jats:italic>z</jats:italic> </jats:sub>, and an outmost layer containing Li<jats:sub>2</jats:sub>CO<jats:sub>3</jats:sub> and organic carbonaceous components. Furthermore, surface cracks are found to be pronounced due to mechanical failures and chemical etching. This work demonstrates a model material to realize the precise measurements of LCO interfacial degradations, which deepens our understanding on the interfacial degradation mechanisms.</jats:p>

<jats:p>We study the quantum-droplet state in a three-dimensional (3D) Bose gas in the presence of 1D spin-orbit coupling and Raman coupling, especially the stripe phase with density modulation, by numerically computing the ground state energy including the mean-field energy and Lee–Huang–Yang correction. In this droplet state, the stripe can exist in a wider range of Raman coupling, compared with the BEC-gas state. More intriguingly, both spin-orbit coupling and Raman coupling strengths can be used to tune the droplet density.</jats:p>

<jats:p>We apply supervised machine learning to study the topological states of one-dimensional non-Hermitian systems. Unlike Hermitian systems, the winding number of such non-Hermitian systems can take half integers. We focus on a non-Hermitian model, an extension of the Su–Schrieffer–Heeger model. The non-Hermitian model maintains the chiral symmetry. We find that trained neuron networks can reproduce the topological phase diagram of our model with high accuracy. This successful reproduction goes beyond the parameter space used in the training process. Through analyzing the intermediate output of the networks, we attribute the success of the networks to their mastery of computation of the winding number. Our work may motivate further investigation on the machine learning of non-Hermitian systems.</jats:p>

<jats:p>As a foundation of quantum physics, uncertainty relations describe ultimate limit for the measurement uncertainty of incompatible observables. Traditionally, uncertainty relations are formulated by mathematical bounds for a specific state. Here we present a method for geometrically characterizing uncertainty relations as an entire area of variances of the observables, ranging over all possible input states. We find that for the pair of position and momentum operators, Heisenberg’s uncertainty principle points exactly to the attainable area of the variances of position and momentum. Moreover, for finite-dimensional systems, we prove that the corresponding area is necessarily semialgebraic; in other words, this set can be represented via finite polynomial equations and inequalities, or any finite union of such sets. In particular, we give the analytical characterization of the areas of variances of (a) a pair of one-qubit observables and (b) a pair of projective observables for arbitrary dimension, and give the first experimental observation of such areas in a photonic system.</jats:p>

<jats:p>A novel method for constructing a kernel for the meson bound-state problem is described. It produces a closed form that is symmetry-consistent (discrete and continuous) with the gap equation defined by any admissible gluon-quark vertex, <jats:italic>Γ</jats:italic>. Applicable even when the diagrammatic content of <jats:italic>Γ</jats:italic> is unknown, the scheme can foster new synergies between continuum and lattice approaches to strong interactions. The framework is illustrated by showing that the presence of a dressed-quark anomalous magnetic moment in <jats:italic>Γ</jats:italic>, an emergent feature of strong interactions, can remedy many defects of widely used meson bound-state kernels, including the mass splittings between vector and axial-vector mesons and the level ordering of pseudoscalar and vector meson radial excitations.</jats:p>

<jats:p>Inspired by the <jats:italic>P<jats:sub>cs</jats:sub> </jats:italic>(4459) reported by the LHCb collaboration recently, we investigate the <jats:italic>P<jats:sub>cs</jats:sub> </jats:italic>(4459) production from <jats:italic>Ξ<jats:sub>b</jats:sub> </jats:italic> decay in a molecular scenario using an effective Lagrangian approach. With different <jats:italic>J<jats:sup>P</jats:sup> </jats:italic> assignments to <jats:italic>P<jats:sub>cs</jats:sub> </jats:italic>(4459), the magnitude of branching fractions of <jats:italic>Ξ<jats:sub>b</jats:sub> </jats:italic> → <jats:italic>P<jats:sub>cs</jats:sub> </jats:italic>(4459) <jats:italic>K</jats:italic> is estimated, which is of the order of 10<jats:sup>−4</jats:sup>. Together with the decay properties of <jats:italic>P<jats:sub>cs</jats:sub> </jats:italic>(4459), the present estimations could be further testified by precise measurements and contribute to a better understanding of the molecular interpretations and the exploration of <jats:italic>J<jats:sup>P</jats:sup> </jats:italic> quantum numbers of <jats:italic>P<jats:sub>cs</jats:sub> </jats:italic>(4459).</jats:p>

<jats:p>We periodically modulate the lattice trapping potential of a <jats:sup>87</jats:sup>Sr optical clock to Floquet engineer the clock transition. In the context of atomic gases in lattices, Floquet engineering has been used to shape the dispersion and topology of Bloch quasi-energy bands. Differently from these previous works manipulating the external (spatial) quasi-energies, we target the internal atomic degrees of freedom. We shape Floquet spin quasi-energies and measure their resonance profiles with Rabi spectroscopy. We provide the spectroscopic sensitivity of each band by measuring the Fisher information and show that this is not depleted by the Floquet dynamical modulation. The demonstration that the internal degrees of freedom can be selectively engineered by manipulating the external degrees of freedom inaugurates a novel device with potential applications in metrology, sensing and quantum simulations.</jats:p>

<jats:p>Above-band-gap optical excitation of electron-hole pairs screens the doping-induced surface electric field and generates terahertz (THz) pulses via free-carrier transport. THz emission from a heavily doped silicon surface is much weaker than that of lightly doped samples. A polarity reversal of the THz electric field is observed in heavily doped p-type silicon, indicating that the doping related and carrier induced surface electric fields oppose each other. By comparing the penetration depth of the excitation laser with the thickness of the depletion layer for the doped silicon, it is shown that competition between diffusion and drift current causes the polarity reversal.</jats:p>

<jats:p>We demonstrated a nonlinear temporal filter based on the self-diffraction (SD) process. Temporal contrast enhancement, angular dispersion and spectrum broadening properties of the SD process are investigated in experiment and simulation. Driven by spectral phase well compensated laser pulses with bandwidth of 28 nm, the filter produced clean pulses with a temporal contrast higher than 10<jats:sup>10</jats:sup> and excellent spatial profile, the spectrum of which was smoothed and broadened to 64 nm. After implementing this filter into a home-made 30 TW Ti:sapphire amplifier, temporal contrast of the amplified pulses was enhanced to 10<jats:sup>10</jats:sup> within the time scale of –400 ps.</jats:p>