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<jats:p>We investigate the structural variation and physical properties of layered La<jats:sub>2</jats:sub> <jats:italic>M</jats:italic> <jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>O<jats:sub>2</jats:sub> (<jats:italic>M</jats:italic> = Cu, Ni) compound upon Co doping. It is found that the substitution of Co ion just induces the monotonous change of lattice constants without observing the anomalous kink in superconducting La<jats:sub>2</jats:sub>(Cu<jats:sub>1–<jats:italic>x</jats:italic> </jats:sub>Ni<jats:sub> <jats:italic>x</jats:italic> </jats:sub>)<jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>O<jats:sub>2</jats:sub> solid-solutions. Meanwhile, this doping barely changes As–As bond length in [<jats:italic>M</jats:italic> <jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>]<jats:sup>2–</jats:sup> subunit (±2%), being significantly smaller than 7% shrinkage of that in La<jats:sub>2</jats:sub>(Cu<jats:sub>1–<jats:italic>x</jats:italic> </jats:sub>Ni<jats:sub> <jats:italic>x</jats:italic> </jats:sub>)<jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>O<jats:sub>2</jats:sub>. Therefore, the doping dependence of crystal structure exhibits similar trend with Ba<jats:sub>1–<jats:italic>x</jats:italic> </jats:sub>K<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub> without the interference of As1–As2 bonding, implying that the Co substitution for Cu/Ni is hole-doped. In terms of physical property, La<jats:sub>2</jats:sub>(Cu<jats:sub>1–<jats:italic>x</jats:italic> </jats:sub>Co<jats:sub> <jats:italic>x</jats:italic> </jats:sub>)<jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>O<jats:sub>2</jats:sub> turns into itinerant ferromagnetic metal, while La<jats:sub>2</jats:sub>(Ni<jats:sub>1–<jats:italic>x</jats:italic> </jats:sub>Co<jats:sub> <jats:italic>x</jats:italic> </jats:sub>)<jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>O<jats:sub>2</jats:sub> shows paramagnetism and suppressed structural phase transition upon Co-doping. The distinct structural variation and absence of superconductivity provide important clues to understand the effect of As–As bond in [<jats:italic>M</jats:italic> <jats:sub>5</jats:sub>As<jats:sub>3</jats:sub>]<jats:sup>2–</jats:sup> subunit.</jats:p>

<jats:p>Co<jats:sub>3</jats:sub>Sn<jats:sub>2</jats:sub>S<jats:sub>2</jats:sub> has attracted a lot of attention for its multiple novel physical properties, including topological nontrivial surface states, anomalous Hall effect, and anomalous Nernst effect. Vacancies, which play important roles in functional materials, have attracted increasing research attention. In this paper, by using density functional theory calculations, we first obtain band structures and magnetic moments of Co<jats:sub>3</jats:sub>Sn<jats:sub>2</jats:sub>S<jats:sub>2</jats:sub> with exchange-correlation functionals at different levels. It is found that the generalized gradient approximation gives the positions of Weyl points consistent with experiments in bulk Co<jats:sub>3</jats:sub>Sn<jats:sub>2</jats:sub>S<jats:sub>2</jats:sub>. We then investigate the electronic structures of defects on surfaces with S and Sn terminations which have been observed in experiments. The results show that the single sulfur vacancy on the S-terminated surface introduces localized bond states inside the bandgap near the Fermi level. For di- and tri-sulfur vacancies, the localized defect states hybridize with neighboring ones, forming bonding states as well as anti-bonding states. The Sn vacancy on the Sn-terminated surface also introduces localized bond states, which are merged with the valence bands. These results provide a reference for future experimental investigations of vacancies in Co<jats:sub>3</jats:sub>Sn<jats:sub>2</jats:sub>S<jats:sub>2</jats:sub>.</jats:p>

<jats:p>The self-catalyzed growth of GaAs nanowires (NWs) on silicon (Si) is an effective way to achieve integration between group III–V elements and Si. High-crystallinity uniform GaAs NW arrays were grown by solid-source molecular beam epitaxy (MBE). In this paper, we describe systematic experiments which indicate that the substrate treatment is crucial to the highly crystalline and uniform growth of one-dimensional nanomaterials. The influence of natural oxidation time on the crystallinity and uniformity of GaAs NW arrays was investigated and is discussed in detail. The GaAs NW crystallinity and uniformity are maximized after 20 days of natural oxidation time. This work provides a new solution for producing high-crystallinity uniform III–V nanowire arrays on wafer-scale Si substrates. The highly crystalline uniform NW arrays are expected to be useful for NW-based optical interconnects and Si platform optoelectronic devices.</jats:p>

<jats:p>Multiple steady solutions and hysteresis phenomenon in the square cavity flows driven by the surface with antisymmetric velocity profile are investigated by numerical simulation and bifurcation analysis. A high order spectral element method with the matrix-free pseudo-arclength technique is used for the steady-state solution and numerical continuation. The complex flow patterns beyond the symmetry-breaking at <jats:italic>Re</jats:italic> ≃ 320 are presented by a bifurcation diagram for <jats:italic>Re</jats:italic> &lt; 2500. The results of stable symmetric and asymmetric solutions are consistent with those reported in literature, and a new unstable asymmetric branch is obtained besides the stable branches. A novel hysteresis phenomenon is observed in the range of 2208 &lt; <jats:italic>Re</jats:italic> &lt; 2262, where two pairs of stable and two pairs of unstable asymmetric steady solutions beyond the stable symmetric state coexist. The vortices near the sidewall appear when the Reynolds number increases, which correspond to the bifurcation of topology structure, but not the bifurcation of Navier–Stokes equations. The hysteresis is proposed to be the result of the combined mechanisms of the competition and coalescence of secondary vortices.</jats:p>

<jats:p>The response of uniaxial anisotropic ferromagnetic particles with linear reaction dynamics subjected to alternating current (AC) or direct current (DC) bias magnetic field is evaluated by the reaction–diffusion equation for the probability distribution function of the molecular concentration in the spherical coordinate system. The magnetization function and the probability distribution function of the magnetic particles in the reaction system are derived by using the Legendre polynomials and Laplace transform. We discuss the characteristics of magnetization and probability distribution of the magnetic particles with different anisotropic parameters driven by a DC and AC magnetic fields, respectively. It is shown that both the magnetization and the probability distribution decrease with time increasing due to the reaction process. The uniformity of the probability distribution and the amplitude of the magnetization are both affected by the anisotropic parameters. Meanwhile, the difference between the case with linear reaction dynamics and the non-reaction case is discussed.</jats:p>

<jats:p>Quantum speed limit and entanglement of a two-spin Heisenberg <jats:italic>XYZ</jats:italic> system in an inhomogeneous external magnetic field are investigated. The physical system studied is the excess electron spin in two adjacent quantum dots. The influences of magnetic field inhomogeneity as well as spin–orbit coupling are studied. Moreover, the spin interaction with surrounding magnetic environment is investigated as a non-Markovian process. The spin–orbit interaction provides two important features: the formation of entanglement when two qubits are initially in a separated state and the degradation and rebirth of the entanglement.</jats:p>

<jats:p>Due to the unavoidable interaction between the quantum channel and its ambient environment, it is difficult to generate and maintain the maximally entanglement. Thus, the research on multiparty information transmission via non-maximally entangled channels is of academic value and general application. Here, we utilize the non-maximally entangled channels to implement two multiparty remote state preparation schemes for transmitting different quantum information from one sender to two receivers synchronously. The first scheme is adopted to transmit two different four-qubit cluster-type entangled states to two receivers with a certain probability. In order to improve success probabilities of such multicast remote state preparation using non-maximally entangled channels, we put forward the second scheme, which deals with the situation that is a synchronous transfer of an arbitrary single-qubit state and an arbitrary two-qubit state from one sender to two receivers. In particular, its success probability can reach 100% in principle, and independent of the entanglement degree of the shared non-maximally entangled channel. Notably, in the second scheme, the auxiliary particle is not required.</jats:p>

<jats:p>We report a novel method to prepare a mixture of <jats:sup>40</jats:sup>K Fermi gas having an equal population of the two ground magnetic spin states confined in an optical dipole trap, in the presence of an noisy quantization (magnetic) field. We realize the equal population mixture by applying a series of RF pulses. We observe the dependence of the population distribution between two spin states on the number of the applied RF pulses and find that the decoherence effects leading to the population fluctuations are overcome by the high number of RF pules. Our demonstrated technique can be potentially used in the precision measurement experiments with ultracold gases in noisy environments.</jats:p>

<jats:p>We investigate the advantage of coherent superposition of two different coded channels in quantum metrology. In a continuous variable system, we show that the Heisenberg limit 1/<jats:italic>N</jats:italic> can be beaten by the coherent superposition without the help of indefinite causal order. And in parameter estimation, we demonstrate that the strategy with the coherent superposition can perform better than the strategy with quantum <jats:sc>switch</jats:sc> which can generate indefinite causal order. We analytically obtain the general form of estimation precision in terms of the quantum Fisher information and further prove that the nonlinear Hamiltonian can improve the estimation precision and make the measurement uncertainty scale as 1/<jats:italic>N<jats:sup>m</jats:sup> </jats:italic> for <jats:italic>m</jats:italic> ≥ 2. Our results can help to construct a high-precision measurement equipment, which can be applied to the detection of coupling strength and the test of time dilation and the modification of the canonical commutation relation.</jats:p>

<jats:p>We propose an optimized cluster density matrix embedding theory (CDMET). It reduces the computational cost of CDMET with simpler bath states. And the result is as accurate as the original one. As a demonstration, we study the distant correlations of the Heisenberg <jats:italic>J</jats:italic> <jats:sub>1</jats:sub>–<jats:italic>J</jats:italic> <jats:sub>2</jats:sub> model on the square lattice. We find that the intermediate phase (0.43 ≲ <jats:italic>J</jats:italic> <jats:sub>2</jats:sub> ≲ 0.62) is divided into two parts. One part is a near-critical region (0.43 ≲ <jats:italic>J</jats:italic> <jats:sub>2</jats:sub> ≲ 0.50). The other part is the plaquette valence bond solid (PVB) state (0.51 ≲ <jats:italic>J</jats:italic> <jats:sub>2</jats:sub> ≲ 0.62). The spin correlations decay exponentially as a function of distance in the PVB.</jats:p>