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<jats:p>The search for new two-dimensional (2D) harvesting materials that directly convert (waste) heat into electricity has received increasing attention. In this work, thermoelectric (TE) properties of monolayer square-Au<jats:sub>2</jats:sub>S are accurately predicted using a parameter-free <jats:italic>ab initio</jats:italic> Boltzmann transport formalism with fully considering the spin–orbit coupling (SOC), electron–phonon interactions (EPIs), and phonon–phonon scattering. It is found that the square-Au<jats:sub>2</jats:sub>S monolayer is a promising room-temperature TE material with an n-type (p-type) figure of merit <jats:italic>ZT</jats:italic> = 2.2 (1.5) and an unexpected high n-type <jats:italic>ZT</jats:italic> = 3.8 can be obtained at 600 K. The excellent TE performance of monolayer square-Au<jats:sub>2</jats:sub>S can be attributed to the ultralow lattice thermal conductivity originating from the strong anharmonic phonon scattering and high power factor due to the highly dispersive band edges around the Fermi level. Additionally, our analyses demonstrate that the explicit treatments of EPIs and SOC are highly important in predicting the TE properties of monolayer square-Au<jats:sub>2</jats:sub>S. The present findings will stimulate further the experimental fabrication of monolayer square-Au<jats:sub>2</jats:sub>S-based TE materials and offer an in-depth insight into the effect of SOC and EPIs on TE transport properties.</jats:p>

<jats:p>The influence of the off-resonant circularly polarized light on the Josephson current in the time-reversal broken superconducting Weyl semimetal junctions is investigated by using the Bogoliubov–de Gennes equation and the transfer matrix approach. Both the zero momentum BCS pairing states and the finite momentum Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) pairing states are considered for the Weyl superconductors. When a circularly polarized light is applied, it is shown that the current phase relation remains unchanged for the BCS pairing with the increasing of incident radiation intensity <jats:italic>A</jats:italic> <jats:sub>0</jats:sub>. For FFLO pairing, the Josephson current exhibits the 0–<jats:italic>π</jats:italic> transition and periodic oscillation as a function of <jats:italic>A</jats:italic> <jats:sub>0</jats:sub>. The dependence of free energy and critical current on <jats:italic>A</jats:italic> <jats:sub>0</jats:sub> are also investigated.</jats:p>

<jats:p>The magnetism and magnetocaloric effect (MCE) of rare-earth-based tungstate compounds <jats:italic>R</jats:italic> <jats:sub>3</jats:sub>BWO<jats:sub>9</jats:sub> (<jats:italic>R</jats:italic> = Gd, Dy, Ho) have been studied by magnetic susceptibility, isothermal magnetization, and specific heat measurements. No obvious long-range magnetic ordering can be found down to 2 K. The Curie–Weiss fitting and magnetic susceptibilities under different applied fields reveal the existence of weak short-range antiferromagnetic couplings at low temperature in these systems. The calculations of isothermal magnetization exhibit a giant MCE with the maximum changes of magnetic entropy being 54.80 J/kg⋅K at 2 K for Gd<jats:sub>3</jats:sub>BWO<jats:sub>9</jats:sub>, 28.5 J/kg⋅K at 6 K for Dy<jats:sub>3</jats:sub>BWO<jats:sub>9</jats:sub>, and 29.76 J/kg⋅K at 4 K for Ho<jats:sub>3</jats:sub>BWO<jats:sub>9</jats:sub>, respectively, under a field change of 0–7 T. Especially for Gd<jats:sub>3</jats:sub>BWO<jats:sub>9</jats:sub>, the maximum value of magnetic entropy change (<jats:inline-formula> <jats:tex-math><?CDATA $-\Delta {S}_{M}^{\max }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>−</mml:mo> <mml:mo>Δ</mml:mo> <mml:msubsup> <mml:mi>S</mml:mi> <mml:mi>M</mml:mi> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_7_077501_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) and adiabatic temperature change (<jats:inline-formula> <jats:tex-math><?CDATA $-\Delta {T}_{{\rm{ad}}}^{\max }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>−</mml:mo> <mml:mo>Δ</mml:mo> <mml:msubsup> <mml:mi>T</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">ad</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_7_077501_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>) are 36.75 J/kg⋅K and 5.56 K for a low field change of 0–3 T, indicating a promising application for low temperature magnetic refrigeration.</jats:p>

<jats:p>The single crystals of Nd<jats:sub>0.5</jats:sub>Pr<jats:sub>0.5</jats:sub>FeO<jats:sub>3</jats:sub> were successfully grown by optical floating zone method. Room temperature x-ray diffraction and Laue photograph declared the homogeneity and high quality of the crystal. The significant magnetic anisotropy and multiple magnetic transitions illustrate the complex magnetic structure. At high temperatures (<jats:italic>T</jats:italic> &gt; 66 K), it shows the typical characteristics of <jats:italic>Γ</jats:italic> <jats:sub>4</jats:sub>(G<jats:sub> <jats:italic>x</jats:italic> </jats:sub>, A<jats:sub> <jats:italic>y</jats:italic> </jats:sub>, F<jats:sub> <jats:italic>z</jats:italic> </jats:sub>) state. With the decrease of the temperature, it undergoes a first-order spin reorientation transition from <jats:italic>Γ</jats:italic> <jats:sub>4</jats:sub>(G<jats:sub> <jats:italic>x</jats:italic> </jats:sub>, A<jats:sub> <jats:italic>y</jats:italic> </jats:sub>, F<jats:sub> <jats:italic>z</jats:italic> </jats:sub>) to <jats:italic>Γ</jats:italic> <jats:sub>2</jats:sub>(F<jats:sub> <jats:italic>x</jats:italic> </jats:sub>, C<jats:sub> <jats:italic>y</jats:italic> </jats:sub>, G<jats:sub> <jats:italic>z</jats:italic> </jats:sub>) state in the temperature window of 45–66 K under an applied magnetic field of 0.01 T. As the temperature drops to ∼ 17 K, a new magnetic interaction mechanism works, which results in a further enhancement of magnetization. The <jats:italic>T</jats:italic>–<jats:italic>H</jats:italic> phase diagram of Nd<jats:sub>0.5</jats:sub>Pr<jats:sub>0.5</jats:sub>FeO<jats:sub>3</jats:sub> single crystal was finally constructed.</jats:p>

<jats:p>A numerical study reports that the zero-field skyrmions in FeGe thin films are stabilized when a FeGe layer is exchange coupled to a single-domain Ni layer, which has been magnetized perpendicularly. Due to the small thickness, an easy-plane anisotropy in the FeGe layer is taken into account, and the skyrmion-crystal state is favored to appear for low anisotropies and intermediate FeGe/Ni interlayer exchange couplings, and finally transformed from a labyrinth-like and into an out-of-plane uniform state for the large couplings or into an in-plane state for the high anisotropies. Furthermore, the maximum skyrmion charge number is bigger for the periodic and fixed boundary conditions with an out-of-plane magnetization; on the contrary, the Bloch-type skyrmions can be frozen and stabilized for the larger couplings on the fixed boundary with an in-plane magnetization, similar to the experimental results of the magnetic-field-induced skyrmions. Finally, the skyrmion charge number and diameter both decrease if the nonmagnetic defects exist, and the skyrmion centers are prone to being captured by defect sites. This work evidences that the ensembles of homochiral skyrmions stabilized in the multilayers fabricated by well-established technologies present a roadmap to design new classes of the materials that can host skyrmions.</jats:p>

<jats:p>In order to counteract the demagnetization caused by eddy current loss, widespread attention has been devoted to increasing the resistivity of permanent magnets. We prepared 2:17-type SmCo magnets doped with different ZrO<jats:sub>2</jats:sub> contents and investigated the influence of the ZrO<jats:sub>2</jats:sub> content on the magnetic properties and resistive anisotropism. The results showed that not only was the resistivity of the magnet improved, but, in addition, the coercivity of the magnet was significantly increased. The microstructure was studied with TEM, which showed that ZrO<jats:sub>2</jats:sub> doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures. The increased grain boundaries and Sm<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> phases were favorable to the improvement of resistivity. The decrease of the lamellar phases caused a narrowing of the resistive anisotropism. The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of <jats:italic>H</jats:italic> <jats:sub>cj</jats:sub>. However, an excessive amount caused an increase of the Zr<jats:sub>6</jats:sub>(FeCo)<jats:sub>23</jats:sub> phase and a deterioration of the cellular structure, thereby leading to a decrease in coercivity.</jats:p>

<jats:p>We study the magnon bands of twisted bilayer honeycomb quantum magnets using linear spin wave theory. Although the interlayer coupling can be ferromagnetic or antiferromagnetic, we keep the intralayer one ferromagnetic to avoid possible frustration. For the interlayer ferromagnetic case, we find the magnon bands have similar features with the corresponding electronic energy spectrums. Although the linear dispersions near the Dirac points are preserved in the magnon bands of twisted bilayer magnets, their slopes are reduced with the decrease of the twist angles. On the other hand, the interlayer antiferromagnetic couplings generate quite different magnon spectra. The two single-layered magnon spectra are usually decoupled due to the opposite orientations of the spins in the two layers. We also develop a low-energy continuous theory for very small twist angles, which has been verified to fit well with the exact tight-binding calculations. Our results may be experimentally observed due to the rapid progress in two-dimensional magnetic materials.</jats:p>

<jats:p>We propose a kind of spectral polarization-encoding (SPE) for broadband light pulses, which is realized by inducing optical rotatory dispersion (ORD), and decoded by compensating ORD. Combining with polarization-sensitive devices, SPE can not only work to control polarization-dependent transmission for central wavelength or bandwidth-tunable filtering, but also can be used for broadband regenerative or multi-pass amplification with a polarization-dependent gain medium to improve output bandwidth. SPE is entirely passive thus very simple to be designed and aligned. By using an ORD crystal with a good transmission beyond 3-μm mid-infrared region, <jats:italic>e.g.</jats:italic>, AgGaS<jats:sub>2</jats:sub>, SPE promises to be applied for the wavelength tuning lasers in mid-infrared region, where the tunning devices are rather under developed compared with those in visible and near-infrared region.</jats:p>

<jats:p>Graphite carbon nitride (g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub>) attracts wide-ranging research interest due to its extraordinary physicochemical properties and promising applications ranging from heterogeneous catalysis to fuel cells. In this work, we design different g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub>-based quantum dots (gCNQDs), carry out a systematic study of optical properties, and elucidate the shape selectivity, composite nanostructure, and outfield effect. In particular, composites of gCNQDs and metal nanochains present excellent optical response, making it applicable to bioimaging, nano-plasma devices, and metalloenzyme in infrared light related fields. Besides, QDs which original bridging nitrogen atoms are replaced by amino (–NH<jats:sub>2</jats:sub>), hydroxyl (–OH), and methyl (–CH<jats:sub>3</jats:sub>) functional groups respectively, have excellent spectral selectivity in the deep ultraviolet region. More interestingly, in the study of the laser interaction with materials, the gCNQDs exhibit extremely high stability and light corrosion resistance. Phase transition from insulation to metal is observed under the critical condition of about 5 eV intensity or 337 nm wavelength. All provided theoretical support for designs and applications in g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> quantum devices.</jats:p>

<jats:p>We study the magneto-optical conductivity of a number of van der Waals heterostructures, namely, twisted bilayer graphene, AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride. As the magnetic field increases, the absorption spectrum exhibits a self-similar recursive pattern reflecting the fractal nature of the energy spectrum. Whilst twisted bilayer graphene displays only weak circular dichroism, the other four structures display strong circular dichroism with monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride being particularly pronounced owing to strong inversion symmetry breaking properties of the hexagonal boron nitride layer. As the left and right circularly polarized light interact with these structures differently, plane-polarized incident light undergoes a Faraday rotation and gains an ellipticity when transmitted. The size of the respective angles is on the order of a degree.</jats:p>