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<jats:p>We systematically measure the superconducting (SC) and mixed state properties of high-quality CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> single crystals with <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> ∼ 3.5 K. We find that the upper critical field <jats:italic>H</jats:italic> <jats:sub>c2</jats:sub>(<jats:italic>T</jats:italic>) exhibits a large anisotropic ratio of <jats:inline-formula> <jats:tex-math> <?CDATA ${H}_{{\rm{c}}2}^{ab}/{H}_{{\rm{c}}2}^{c}\sim 9$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>a</mml:mi> <mml:mi>b</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>/</mml:mo> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> <mml:mn>2</mml:mn> </mml:mrow> <mml:mi>c</mml:mi> </mml:msubsup> <mml:mo>∼</mml:mo> <mml:mn>9</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_5_057403_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at zero temperature and fitting its temperature dependence requires a minimum two-band effective model. Moreover, the ratio of the lower critical field, <jats:inline-formula> <jats:tex-math> <?CDATA ${H}_{{\rm{c}}1}^{ab}/{H}_{{\rm{c}}1}^{c}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>a</mml:mi> <mml:mi>b</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>/</mml:mo> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> <mml:mn>1</mml:mn> </mml:mrow> <mml:mi>c</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_5_057403_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, is also found to be larger than 1, which indicates that the in-plane energy dispersion is strongly renormalized near Fermi energy. Both <jats:italic>H</jats:italic> <jats:sub>c1</jats:sub>(<jats:italic>T</jats:italic>) and SC diamagnetic signal are found to change little initially below <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> ∼ 3.5 K and then to increase abruptly upon cooling to a characteristic temperature of ∼2.8 K. Furthermore, we identify a two-fold anisotropy of in-plane angular-dependent magnetoresistance in the mixed state. Interestingly, we find that, below the same characteristic <jats:italic>T</jats:italic> ∼ 2.8 K, the orientation of this two-fold anisotropy displays a peculiar twist by an angle of 60° characteristic of the Kagome geometry. Our results suggest an intriguing superconducting state emerging in the complex environment of Kagome lattice, which, at least, is partially driven by electron-electron correlation.</jats:p>

<jats:p>High resolution angle-resolved photoemission spectroscopy (ARPES) measurements are carried out on CaKFe<jats:sub>4</jats:sub>As<jats:sub>4</jats:sub>, KCa<jats:sub>2</jats:sub>Fe<jats:sub>4</jats:sub>As<jats:sub>4</jats:sub>F<jats:sub>2</jats:sub> and (Ba<jats:sub>0.6</jats:sub>K<jats:sub>0.4</jats:sub>)Fe<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub> superconductors. Clear evidence of band folding between the Brillouin zone center and corners with a (<jats:italic>π</jats:italic>,<jats:italic>π</jats:italic>) wave vector has been found from the measured Fermi surface and band structures in all the three kinds of superconductors. A dominant <jats:inline-formula> <jats:tex-math> <?CDATA $\sqrt{2}\times \sqrt{2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msqrt> <mml:mn>2</mml:mn> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mn>2</mml:mn> </mml:msqrt> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_5_057404_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> surface reconstruction is observed on the cleaved surface of CaKFe<jats:sub>4</jats:sub>As<jats:sub>4</jats:sub> by scanning tunneling microscopy (STM) measurements. We propose that the commonly observed <jats:inline-formula> <jats:tex-math> <?CDATA $\sqrt{2}\times \sqrt{2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msqrt> <mml:mn>2</mml:mn> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mn>2</mml:mn> </mml:msqrt> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_38_5_057404_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> reconstruction in the FeAs-based superconductors provides a general scenario to understand the origin of the (<jats:italic>π</jats:italic>,<jats:italic>π</jats:italic>) band folding. Our observations provide new insights in understanding the electronic structure and superconductivity mechanism in iron-based superconductors.</jats:p>

<jats:p>We show that a suitable combination of flat-band ferromagnetism, geometry and nontrivial electronic band topology can give rise to itinerant topological magnons. An <jats:italic>SU</jats:italic>(2) symmetric topological Hubbard model with nearly flat electronic bands, on a Kagome lattice, is considered as the prototype. This model exhibits ferromagnetic order when the lowest electronic band is half-filled. Using the numerical exact diagonalization method with a projection onto this nearly flat band, we can obtain the magnonic spectra. In the flat-band limit, the spectra exhibit distinct dispersions with Dirac points, similar to those of free electrons with isotropic hoppings, or a local spin magnet with pure ferromagnetic Heisenberg exchanges on the same geometry. Significantly, the non-flatness of the electronic band may induce a topological gap at the Dirac points, leading to a magnonic band with a nonzero Chern number. More intriguingly, this magnonic Chern number changes its sign when the topological index of the electronic band is reversed, suggesting that the nontrivial topology of the magnonic band is related to its underlying electronic band. Our work suggests interesting directions for the further exploration of, and searches for, itinerant topological magnons.</jats:p>

<jats:p>Magnon–magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies. To induce magnon–magnon coupling, the parity symmetry between two magnetization needs to be broken. Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure. We successfully introduce a magnon–magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(<jats:italic>t</jats:italic> <jats:sub>Ir</jats:sub> = 0.6 nm, 1.2 nm)/CoFeB(13 nm). Remarkably, we find that the weakly uniaxial anisotropy field (∼ 20 Oe) makes the magnon–magnon coupling anisotropic. The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for <jats:italic>t</jats:italic> <jats:sub>Ir</jats:sub> = 0.6 nm, and between 0.09 GHz and 1.4 GHz for <jats:italic>t</jats:italic> <jats:sub>Ir</jats:sub> = 1.2 nm. Our results demonstrate a feasible way to induce magnon–magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field. The magnon–magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.</jats:p>

<jats:p>The V<jats:sub>2</jats:sub>C compound, belonging to the group of two-dimensional transition metal carbonitrides, or MXenes, has demonstrated a promising electrochemical performance in capacitor applications in acidic electrolytes; however, there is evidence to suggest that V<jats:sub>2</jats:sub>C is unstable in an acidic environment. On the other hand, the performance of V<jats:sub>2</jats:sub>C in neutral aqueous electrolytes is still moderate, and has not yet been systematically studied. The charge storage mechanism in a V<jats:sub>2</jats:sub>C electrode, employed in neutral aqueous electrolytes, is investigated via cyclic voltammetry testing and <jats:italic>in situ</jats:italic> x-ray diffraction (XRD). Good specific capacitances are achieved, specifically 208 F/g in 0.5 M Li<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>, 225 F/g in 1 M MgSO<jats:sub>4</jats:sub>, 120 F/g in 1M Na<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>, and 104 F/g in 0.5 M K<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>. Using <jats:italic>in situ</jats:italic> XRD, we observe that, during the charge and discharge process, the <jats:italic>c</jats:italic>-lattice parameter shrinks or expands by up to 0.25 Å in MgSO<jats:sub>4</jats:sub>, and 0.29 Å in Li<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub> which demonstrates the intercalation/de-intercalation of cations into the <jats:italic>d</jats:italic>-V<jats:sub>2</jats:sub>C layer.</jats:p>

<jats:p>We demonstrate that the two degenerate energy levels in spin–orbit coupled trapped Bose gases, coupled by a quenched Zeeman field, can be used for angular momentum Josephson effect. In a static quenched field, we can realize a Josephson oscillation with a period ranging from millisecond to hundreds of milliseconds. Moreover, by a driven Zeeman field, we realize a new Josephson oscillation, in which the population imbalance may have the same expression as the current in the direct-current Josephson effect. When the dynamics of the condensate cannot follow up the modulation frequency, it is in the self-trapping regime. This new dynamic is understood from the time-dependent evolution of the constant-energy trajectory in the phase space. This model has several salient advantages compared to the previous ones. The condensates are isolated from their excitations by a finite gap, thus can greatly suppress the damping effect induced by thermal atoms and Bogoliubov excitations. The oscillation period can be tuned by several orders of magnitude without influencing other parameters. In experiments, the dynamics can be mapped out from spin and momentum spaces, thus it is not limited by the spatial resolution in absorption imaging. This system can serve as a promising platform for matter wave interferometry and quantum metrology.</jats:p>

<jats:p>Knot theory provides a powerful tool for understanding topological matters in biology, chemistry, and physics. Here knot theory is introduced to describe topological phases in a quantum spin system. Exactly solvable models with long-range interactions are investigated, and Majorana modes of the quantum spin system are mapped into different knots and links. The topological properties of ground states of the spin system are visualized and characterized using crossing and linking numbers, which capture the geometric topologies of knots and links. The interactivity of energy bands is highlighted. In gapped phases, eigenstate curves are tangled and braided around each other, forming links. In gapless phases, the tangled eigenstate curves may form knots. Our findings provide an alternative understanding of phases in the quantum spin system, and provide insights into one-dimension topological phases of matter.</jats:p>

<jats:p>On the basis of <jats:italic>N</jats:italic>-soliton solutions, space-curved resonant line solitons are derived via a new constraint proposed here, for a generalized (2+1)-dimensional fifth-order KdV system. The dynamic properties of these new resonant line solitons are studied in detail. We then discuss the interaction between a resonance line soliton and a lump wave in greater detail. Our results highlight the distinctions between the generalized (2+1)-dimensional fifth-order KdV system and the classical type.</jats:p>

<jats:p>Recently, a relativistic chiral nucleon–nucleon interaction was formulated up to leading order, which provides a good description of the phase shifts of <jats:italic>J</jats:italic> ≤ 1 partial waves [Chin. Phys. C 42 (2018) 014103]. Nevertheless, a separable regulator function that is not manifestly covariant was used in solving the relativistic scattering equation. In the present work, we first explore a covariant and separable form factor to regularize the kernel potential and then apply it to study the simplest but most challenging <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub> channel which features several low-energy scales. In addition to being self-consistent, we show that the resulting relativistic potential can describe quite well the unique features of the <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub> channel at leading order, in particular the pole position of the virtual bound state and the zero amplitude at the scattering momentum ∼ 340 MeV, indicating that the relativistic formulation may be more natural from the viewpoint of effective field theories.</jats:p>

<jats:p>The multi-electron capture and loss cross-sections of Ar<jats:sup>+</jats:sup>–Ne collisions are calculated at absolute energies in the few-keV/a.u. regime. The calculations are performed using a novel inverse collision framework, in the context of a time-dependent density functional theory, combined with molecular dynamics. The extraction of the capture and loss probabilities is based on the particle-number projection technique, originating from nuclear physics, but validly extended to represent many-electron systems. Good agreement between experimental and theoretical data is found, which clearly reveals the non-negligible post-collision decay of the projectile’s electrons, providing further evidence for the applicability of the approach to complex many-electron collision systems.</jats:p>