Beginning with precise data on the ratio of structure functions in deep inelastic scattering (DIS) from $^3$He and $^3$H, collected on the domain $0.19 \leq x_{\scriptscriptstyle{\rm B}} \leq 0.83$, where $x_{\scriptscriptstyle{\rm B}}$ is the Bjorken scaling variable, we employ a robust method for extrapolating such data to arrive at a model-independent result for the $x_{\scriptscriptstyle{\rm B}}=1$ value of the ratio of neutron and proton structure functions. Combining this with information obtained in analyses of DIS from nuclei, corrected for target-structure dependence, we arrive at a prediction for the proton valence-quark ratio: $\left. d_v/u_v \right|_{x_{\scriptscriptstyle{\rm B}}\to 1} = 0.230 (57)$. Requiring consistency with this result presents a challenge to many descriptions of proton structure.

We demonstrate the coherent transfer of an ultrastable optical frequency reference over a 490 km noisy field fiber link. The fiber-induced phase noise power spectrum density per-unit-length at 1 Hz offset frequency can reach up to 510 rad$^2$$\cdot$Hz$^{-1}$$\cdot$km$^{-1}$, which is much higher than the fiber noise observed in previous reports. This extreme level of phase noise is mainly due to the fiber link laying underground along the highway. Appropriate phase-locked loop parameters are chosen to complete the active compensation of fiber noise by measuring the intensity fluctuation of additional phase noise and designing a homemade digital frequency division phase discriminator with a large phase detection range of $2^{12} \pi$ rad. Finally, a noise suppression intensity of approximately 40 dB at 1 Hz is obtained, with fractional frequency instability of $1.1\times10^{-14}$ at 1 s averaging time, and $3.7\times10^{-19}$ at 10000 s. The transfer system will be used for remote atomic clock comparisons and optical frequency distribution over a long-distance communication network established in China.

This work focuses on chirped solitons in a higher-order nonlinear Schrödinger equation, including cubic-quintic-septic nonlinearity, weak nonlocal nonlinearity, self-frequency shift, and self-steepening effect. For the first time, analytical bright and kink solitons, as well as their corresponding chirping, are obtained. The influence of septic nonlinearity and weak nonlocality on the dynamical behaviors of those nonlinearly chirped solitons is thoroughly addressed. The findings of the study give an experimental basis for nonlinear-managed solitons in optical fibers.

Photoelectron momentum distribution in strong-field ionization has a variety of structures that reveal the complicated dynamics of this process. Recently, we identified a low-energy interference structure in the case of a super-intense extreme ultraviolet (XUV) laser pulse and attributed it to the laser-induced electron Fresnel diffraction. This structure is determined by the laser-induced electron displacement [Geng et al. Phys. Rev. A 104 (2021) L021102]. In the present work, we find that the Fresnel diffraction picture also appears in the tunneling and over-barrier regime of ionization by short pulses. However, the electron displacement is now induced by the electric field component of the laser pulse rather than the magnetic field component in the case of the super-intense XUV pulse. After corresponding modifications to our quantum and semiclassical models, we find that the same physical mechanism of the Fresnel diffraction governs the low-energy interference structures along the laser polarization. The results predicted by the two models agree well with the accurate results from the numerical solution to the time-dependent Schrödinger equation.

Uniformly dispersed nickel single atoms (SAs) are experimentally prepared on ultralight N-doped graphene aerogels (Ni-SA@NRGA). The experimental results show that Ni-SAs in graphene aerogels can improve the conduction, polarization losses, and impedance matching properties of the Ni-SA@NRGA. As a result, the minimum reflection loss ($R_{\rm L,min}$) of Ni-SA@NRGA is $-$49.46 dB with a matching thickness of 2.0 mm and the broadest efficient absorption bandwidth is 3.12 GHz at a low thickness of 1.5 mm. Meanwhile, even with a matching thickness of 1.2–2.0 mm, the $R_{\rm L,min}$ value of Ni-SA@NRGA can reach $-$20 dB. The current study demonstrates the significance of incorporating metal single atoms into graphene aerogel for electromagnetic wave absorption.

High-temperature phases of solids are often dynamically stable only. First-principles study of point defects in such solids at 0 K is prohibited by their static instability, which results in random structures of the defect-containing supercell so that the total energy of the supercell is randomly affected by structural distortions far away from the defect. Taking cubic perovskite $\alpha$-CsPbI$_3$ as an example, we first present the problem incurred by the static instability and then propose an approach based on molecular dynamics to carry out ensemble average for tackling the problem. Within affordable simulation time, we obtain converged defect ionization energies, which are unattainable by a standard approach and allow us to evaluate its defect tolerance property. Our work paves the way for studying defects in statically unstable solids.

Owing to the nonequilibrium nature, the energy state of metallic glasses (MGs) can vary a lot and has a critical influence on the physical properties. Exploring new methods to modulate the energy state of glasses and studying its relationship with properties have attracted great interests. Herein, we systematically investigate the energy state, mixing entropy and physical properties of Zr–Ti–Cu–Ni–Be multicomponent high entropy MGs by experiments and simulations. We find that the energy state increases along with the increase of mixing entropy. The yield strength and thermal stability of MGs are also enhanced by high mixing entropy. These results may open a new door on regulation of energy states and thus physical properties of MGs.

Two-dimensional electron gas (2DEG) with high electron mobility is highly desired to study the emergent properties and to enhance future device performance. Here we report the formation of 2DEG with high mobility at the interface between rock-salt BaO and perovskite SrTiO$_{3}$. The interface consists of the ionically compensated BaO$_{1-\delta}$ layer and the electronically compensated TiO$_{2}$ layer, which is demonstrated as a perfect interface without lattice mismatch. The so-formed interface features metallic conductivity with ultralow square resistance of $7.3 \times 10^{-4}\,\Omega /\square$ at 2 K and high residual resistance ratios $R_{\rm 300\,K}/R_{\rm 2\,K}$ up to 4200. The electron mobility reaches 69000 cm$^{2}$$\cdot$V$^{-1}$$\cdot$s$^{-1}$ at 2 K, leading to Shubnikov–de Haas oscillations of resistance. Density functional theory calculations reveal that the effective charge transfers from BaO to the Ti 3$d_{xy}$ orbital occur at the interface, leading to the conducting TiO$_{2}$ layer. Our work unravels that BaO can adapt itself by removing oxygen to minimize the lattice mismatch and to provide substantial carriers to SrTiO$_{3}$, which is the key to forming 2DEGs with high mobility at the interfaces.

Mn-based superconductors are very rare and their superconductivity has only been reported in three-dimensional MnP and quasi-one-dimensional KMn$_{6}$Bi$_{5}$ and RbMn$_{6}$Bi$_{5}$ with [Mn$_{6}$Bi$_{5}$]$^{-}$ columns under high pressures. Here we report the synthesis, magnetism, electrical resistivity, and specific heat capacity of the newly discovered quasi-one-dimensional NaMn$_{6}$Bi$_{5}$. Compared with other $A$Mn$_{6}$Bi$_{5}$ ($A$ = K, Rb, and Cs), NaMn$_{6}$Bi$_{5}$ has abnormal Bi–Bi bond lengths and two antiferromagnetic-like transitions at 47.3 K and 51.8 K. Anisotropic resistivity and low-temperature non-Fermi liquid behavior are observed. Heat capacity measurement reveals that the Sommerfeld coefficient for NaMn$_{6}$Bi$_{5}$ is unusually large. Using first-principles calculations, an unusual enhancement of density of states near the Fermi level is demonstrated for NaMn$_{6}$Bi$_{5}$. The features make NaMn$_{6}$Bi$_{5}$ a more suitable platform to explore the interplay of magnetism and superconductivity.

The CsV$_{3}$Sb$_{5}$ kagome lattice holds the promise for manifesting electron correlation, topology and superconductivity. However, by far only three CsV$_{3}$Sb$_{5}$-like kagome materials have been experimentally spotted. We enlarge this family of materials to 1386 compounds via element species substitution, and the further screening process suggests that 28 promising candidates have superior thermodynamic stability, hence they are highly likely to be synthesizable. Moreover, these compounds possess several unique electronic structures, and can be categorized into five non-magnetic and three magnetic groups accordingly. It is our hope that this work can greatly expand the viable phase space of the CsV$_{3}$Sb$_{5}$-like materials for investigating or tuning the novel quantum phenomena in kagome lattice.

In marginally twisted bilayer graphene, the Moiré pattern consists of the maximized AB (BA) stacking regions, minimized AA stacking regions and triangular networks of domain walls. Here we realize the strain-modulated electronic structures of marginally twisted bilayer graphene by scanning tunneling microscopy/spectroscopy and density functional theory (DFT) calculations. The experimental data show four peaks near the Fermi energy at the AA regions. DFT calculations indicate that the two new peaks closer to the Fermi level may originate from the intrinsic heterostrain and the electric field implemented by back gate is likely to account for the observed shift of the four peaks. Furthermore, the $dI/dV$ map across Moiré patterns with different strain strengths exhibits a distinct appearance of the helical edge states.

As a new type of quantum state of matter hosting low energy relativistic quasiparticles, Weyl semimetals (WSMs) have attracted significant attention for scientific community and potential quantum device applications. In this study, we present a comprehensive investigation of the structural, magnetic, and transport properties of noncentrosymmetric $R$AlSi ($R$ = Sm, Ce), which have been predicted to be new magnetic WSM candidates. Both samples exhibit nonsaturated magnetoresistance, with about 900% and 80% for SmAlSi and CeAlSi, respectively, at temperature of 1.8 K and magnetic field of 9 T. The carrier densities of SmAlSi and CeAlSi exhibit remarkable change around magnetic transition temperatures, signifying that the electronic states are sensitive to the magnetic ordering of rare-earth elements. At low temperatures, SmAlSi reveals prominent Shubnikov–de Haas oscillations associated with the nontrivial Berry phase. High-pressure experiments demonstrate that the magnetic order is robust and survival under high pressure. Our results would yield valuable insights into WSM physics and potentials in applications to next-generation spintronic devices in the $R$AlSi ($R$ = Sm, Ce) family.

We investigate the spin Hall magnetoresistance (SMR) in all-antiferromagnetic heterostructures $\alpha$-Fe$_{2}$O$_{3}$/Cr$_{2}$O$_{3}$ with Pt contacts. When the temperature is ultralow ($ < $ 50 K), the spin current generated in the Pt layer cannot be transmitted through Cr$_{2}$O$_{3}$ ($t = 4$ nm), and the SMR is near zero. Meanwhile, when the temperature is higher than the spin fluctuation temperature $T_{\rm F}$ ($\approx $ 50 K) of Cr$_{2}$O$_{3}$ and lower than its Néel temperature $T_{\rm N}$ ($\approx $ 300 K), the spin current goes through the Cr$_{2}$O$_{3}$ layer and is reflected at the $\alpha$-Fe$_{2}$O$_{3}$/Cr$_{2}$O$_{3}$ interface; an antiferromagnetic (negative) SMR is observed. As temperature increases higher than $T_{\rm N}$, paramagnetic (positive) SMR mainly arises from the spin current reflection at the Cr$_{2}$O$_{3}$/Pt interface. The transition temperatures from negative to positive SMR are enhanced with increasing Cr$_{2}$O$_{3}$ layer thickness, accompanied by the absence of SMR signals when $t = 10$ nm. Such a tunable SMR builds a bridge between spin transport and structures. It also enriches antiferromagnetic spintronics.

Recently, magnetism in two-dimensional (2D) van der Waals (vdW) materials has attracted wide interests. It is anticipated that these materials will stimulate discovery of new physical phenomena and novel applications. The capability to quantitatively measure the magnetism of 2D magnetic vdW materials is essential to understand these materials. Here we report on quantitative measurements of ferromagnetic-to-paramagnetic phase transition of an atomically thin (down to 11 nm) vdW magnet, namely CrBr$_3$, with a Curie point of 37.5 K. This experiment demonstrates that surface magnetism can be quantitatively investigated, which is useful for a wide variety of potential applications.

Nonpolar (11$\bar{2}$0) plane In$_{x}$Ga$_{1- x}$N epilayers comprising the entire In content ($x$) range were successfully grown on nanoscale GaN islands by metal-organic chemical vapor deposition. The structural and optical properties were studied intensively. It was found that the surface morphology was gradually smoothed when $x$ increased from 0.06 to 0.33, even though the crystalline quality was gradually declined, which was accompanied by the appearance of phase separation in the In$_{x}$Ga$_{1- x}$N layer. Photoluminescence wavelengths of 478 and 674 nm for blue and red light were achieved for $x$ varied from 0.06 to 0.33. Furthermore, the corresponding average lifetime ($\tau_{1/e}$) of carriers for the nonpolar InGaN film was decreased from 406 ps to 267 ps, indicating that a high-speed modulation bandwidth can be expected for nonpolar InGaN-based light-emitting diodes. Moreover, the bowing coefficient ($b$) of the (11$\bar{2}$0) plane InGaN was determined to be 1.91 eV for the bandgap energy as a function of $x$.