The synthetic Floquet lattice, generated by multiple strong drives with mutually incommensurate frequencies, provides a powerful platform for quantum simulation of topological phenomena. In this study, we propose a 4-band tight-binding model of the Chern insulator with a Chern number $C=\pm2$ by coupling two layers of the half Bernevig–Hughes–Zhang lattice and subsequently mapping it onto the Floquet lattice to simulate its topological properties. To determine the Chern number of our Floquet-version model, we extend the energy pumping method proposed by Martin et al. [2017 Phys. Rev. X 7 041008] and the topological oscillation method introduced by Boyers et al. [2020 Phys. Rev. Lett. 125 160505], followed by numerical simulations for both methodologies. The simulation results demonstrate the successful extraction of the Chern number using either of these methods, providing an excellent prediction of the phase diagram that closely aligns with the theoretical one derived from the original bilayer half Bernevig–Hughes–Zhang model. Finally, we briefly discuss a potential experimental implementation for our model. Our work demonstrates significant potential for simulating complex topological matter using quantum computing platforms, thereby paving the way for constructing a more universal simulator for non-interacting topological quantum states and advancing our understanding of these intriguing phenomena.

We present a novel approach for generating stable three-dimensional (3D) spatiotemporal solitons (SSs) within a rotating Bose–Einstein condensate, incorporating spin–orbit coupling (SOC), a weakly anharmonic potential and cold Rydberg atoms. This intricate system facilitates the emergence of quasi-stable 3D SSs with topological charges $\left\vert m \right \vert \le 3$ in two spinor components, potentially exhibiting diverse spatial configurations. Our findings reveal that the Rydberg long-range interaction, spin–orbit coupling, and rotational angular frequency exert significant influence on the domains of existence and stability of these solitons. Notably, the Rydberg interaction contributes to a reduction in the norm of topological solitons, while the SOC plays a key role in stabilizing the SSs with finite topological charges. This research of SSs exhibits potential applications in precision measurement, quantum information processing, and other advanced technologies.

Spinor Bose–Einstein condensates (BECs) are formed when atoms in the multi-component BECs possess single hyperfine spin states but retain internal spin degrees of freedom. This study concentrates on a (1+1)-dimensional three-couple Gross–Pitaevskii system to depict the macroscopic spinor BEC waves within the mean-field approximation. Regarding the distribution of the atoms corresponding to the three vertical spin projections, a known binary Darboux transformation is utilized to derive the $N$ matter-wave soliton solutions and triple-pole matter-wave soliton solutions on the zero background, where $N$ is a positive integer. For those multiple matter-wave solitons, the asymptotic analysis is performed to obtain the algebraic expressions of the soliton components in the $N$ matter-wave solitons and triple-pole matter-wave solitons. The asymptotic results indicate that the matter-wave solitons in the spinor BECs possess the property of maintaining their energy content and coherence during the propagation and interactions. Particularly, in the $N$ matter-wave solitons, each soliton component contributes to the phase shifts of the other soliton components; and in the triple-pole matter-wave solitons, stable attractive forces exist between the different matter-wave soliton components. Those multiple matter-wave solitons are graphically illustrated through three-dimensional plots, density plot and contour plot, which are consistent with the asymptotic analysis results. The present analysis may provide the explanations for the complex natural mechanisms of the matter waves in the spinor BECs, and may have potential applications in designs of atom lasers, atom interferometry and coherent atom transport.

$P_c(4457)$ has been discovered over five years, but the parity of this particle remains undetermined. We propose a new interpretation for $P_c(4457)$, which is the state generated from the coupled-channel $\bar{D}^0\varLambda_c^{+}(2595)$ and $\pi^0 P_c(4312)$ since they can exchange an almost on-shell $\varSigma_c^+$. In this scenario, the parity of $P_c(4457)$ will be positive, which is different from the candidate of the bound state of $\bar{D}^*\varSigma_c$. The main decay channel of $P_c(4457)$ in this model is $P_c(4312)\pi$. We propose three processes $\varLambda_b^0 \to J/\psi K_s p \pi^-$, $\varLambda_b^0 \to J/\psi K^- p \pi^0$, and $\varLambda_b^0 \to J/\psi p \pi^- \pi^+ K^-$ to verify $P_c(4457)\to P_c(4312)\pi$.

Metal-free organic emitters, characterized by their thermally activated delayed fluorescence (TADF) properties, offer considerable promise for the creation of highly efficient organic light-emitting diodes (OLEDs). Recently, Shao et al. presented a novel excited state intramolecular proton transfer (ESIPT) system BrA-HBI, demonstrating an emission quantum yield of up to 50% [Adv. Funct. Mater. 32, 2201256 (2022)]. However, many open issues cannot be answered solely by experimental means only and require detailed theoretical investigations. For instance, what causes the activation of TADF from the Keto$^{*}$ tautomer and leads to fluorescence quenching in the Enol$^{*}$ form? Herein, we provide a theoretical investigation on the TADF mechanism of the BrA-HBI molecule by optimally tuned range-separated functionals. Our findings reveal that ESIPT occurs in the BrA-HBI molecule. Moreover, we have disclosed the reason for the fluorescence quenching of the Enol$^{*}$ form and determined that the $T_{2}$ state plays a dominant role in the TADF phenomenon. In addition, double hybrid density functionals method was utilized to verify the reliability of optimally tuned range separation functionals on the calculation of the TADF mechanism in BrA-HBI. These findings not only provide a theoretical reference for development of highly efficient organic light-emitting diodes, but also demonstrate the effectiveness of the optimally tuned range-separated functionals in predicting the luminescence properties of TADF molecules.

Cylindrical vector beams (CVBs) hold significant promise in mode division multiplexing communication owing to their inherent vector mode orthogonality. However, existing studies for facilitating CVB channel processing are confined to mode shift conversions due to their reliance on spin-dependent helical modulations, overlooking the pursuit of mode multiplication conversion. This challenge lies in the multiplicative operation upon inhomogeneous vector mode manipulation, which is expected to advance versatile CVB channel switching and routing. Here, we tackle this gap by introducing a raytracing control strategy that conformally maps the light rays of CVB from the whole annulus distribution to an annular sector counterpart. Incorporated with the multifold conformal annulus-sector mappings and polarization-insensitive phase modulations, this approach facilitates the parallel transformation of input CVB into multiple complementary components, enabling the mode multiplication conversion with protected vector structure. Serving as a demonstration, we experimentally implemented the multiplicative operation of four CVB modes with the multiplier factors of $N=+2$ and $N=-3$, achieving the converted mode purities over 94.24% and 88.37%. Subsequently, 200 Gbit/s quadrature phase shift keying signals were successfully transmitted upon multiplicative switching of four CVB channels, with the bit-error-rate approaching $1\times 10^{-6}$. These results underscore our strategy's efficacy in CVB mode multiplication, which may open promising prospects for its advanced applications.

Materials for deep-ultraviolet (DUV) light emission are extremely rare, significantly limiting the development of efficient DUV light-emitting diodes. Here we report CsMg(I$_{1-x}$Br$_{x}$)$_{3}$ alloys as potential DUV light emitters. Based on rigorous first-principles hybrid functional calculations, we find that CsMgI$_{3}$ has an indirect bandgap, while CsMgBr$_{3}$ has a direct bandgap. Further, we employ a band unfolding technique for alloy supercell calculations to investigate the critical Br concentration in CsMg(I$_{1-x}$Br$_{x}$)$_{3}$ associated with the crossover from an indirect to a direct bandgap, which is found to be $\sim$ 0.36. Thus, CsMg(I$_{1-x}$Br$_{x})_{3}$ alloys with $0.36\leqslant x\leqslant 1$ cover a wide range of direct bandgap (4.38–5.37 eV; 284–231 nm), falling well into the DUV regime. Our study will guide the development of efficient DUV light emitters.

By systematic theoretical calculations, we reveal an excitonic insulator (EI) in the Ta$_2$Pd$_3$Te$_5$ monolayer. The bulk Ta$_2$Pd$_3$Te$_5$ is a van der Waals (vdW) layered compound, whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy. First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke–Johnson functional. Due to the same symmetry of the band-edge states, the two-dimensional polarization $\alpha_{\rm 2D}$ would be finite as the band gap goes to zero, allowing for an EI state in the compound. Using the first-principles many-body perturbation theory, the $GW$ plus Bethe–Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap, indicating the excitonic instability. The computed phonon spectrum suggests that the monolayer is dynamically stable without lattice distortion. Our findings suggest that the Ta$_2$Pd$_3$Te$_5$ monolayer is an excitonic insulator without structural distortion.

As an earth-abundant and environmentally friendly material, tin sulfide (SnS) is not only a high-performance photovoltaic material, but also a new promising thermoelectric material. Despite extensive research on the thermoelectric properties of this material in recent years, the room-temperature thermoelectric figure of merit (ZT) of SnS has not been broke through 2 [2022 Sci. China Mater. 65 1143]. In this work, based on a combination of density functional theory and non-equilibrium Green's function method, the electronic and thermoelectric properties in SnS-nanoribbon-based heterojunctions are studied. The results show that although SnS nanoribbons (SNSNRs) with zigzag edges (ZSNSNRs) and armchair edges (ASNSNRs) both have semiconductor properties, the bandgaps of ASNSNRs are much wider than those of ZSNSNRs, which induces much wider conductance gaps of $N$-ASNSNR ($N$ is the number of tin-sulfide lines across the ribbon width)). In the positive energy region, the ZT peaks of $L$-SNS-Au are much larger than those of $L$-SNS-GNR ($L$ represents the number of longitudinal repeating units of SNSNR in the scattering region). While in the positive energy region, the ZT peaks of $L$-SNS-GNR are larger than those of $L$-SNS-Au. Further calculations reveal that the figure of merit will be over 3.7 in $L$-SNS-Au and 2.2 in $L$-SNS-GNR at room temperature, and over 4 in $L$-SNS-Au and 2.6 in $L$-SNS-GNR at 500 K.

Quasi-one-dimensional (1D) graphene nanoribbons (GNRs) play a crucial role in advancement of next-generation devices. Recent studies have suggested their potential to exhibit unique symmetry-protected topological phases defined by a $Z_2$ invariant. By employing both the tight-binding model and the Floquet theory, our investigation demonstrates the effective control of the topological phase within quasi-1D armchair GNRs (AGNRs) using elliptically polarized light, unveiling rich topological phase diagrams. Specifically, we observe that varying the amplitude of the light can induce transitions in the band gap ($E_{\rm g}$) of AGNRs, leading to multiple changes in the system's $Z_2$ invariant. Furthermore, for heterojunctions composed of different AGNR segments, the junction state can be either created or eliminated by the application of elliptically polarized light.

The chiral $2\times 2$ charge order has been reported and confirmed in the kagome superconductor RbV$_{3}$Sb$_{5}$, while its interplay with superconductivity remains elusive owing to its lowest superconducting transition temperature $T_{\scriptscriptstyle{\rm C}}$ of about 0.85 K in the AV$_{3}$Sb$_{5}$ family (A = K, Rb, Cs) that severely challenges electronic spectroscopic probes. Here, utilizing dilution-refrigerator-based scanning tunneling microscopy down to 30 mK, we observe chiral $2\times 2$ pair density waves with residual Fermi arcs in RbV$_{3}$Sb$_{5}$. We find a superconducting gap of 150 µeV with substantial residual in-gap states. The spatial distribution of this gap exhibits chiral $2\times 2$ modulations, signaling a chiral pair density wave (PDW). Our quasi-particle interference imaging of the zero-energy residual states further reveals arc-like patterns. We discuss the relation of the gap modulations with the residual Fermi arcs under the space-momentum correspondence between PDW and Bogoliubov Fermi states.

La$_{2}$NiO$_{4}$ has a similar structure to La$_{2}$CuO$_{4}$ and was proposed as a high-temperature superconductor based on magnetic-moment measurements decades ago. Nevertheless, with the exception for electrical resistance drop behavior of about 4 orders of magnitude that is claimed to originate from the superconductivity ever observed in Sr-doped La$_{2}$NiO$_{4}$, most electrical data reported to date in La$_{2}$NiO$_{4}$ system exhibit a trivial insulating ground state. Here, we definitively identify the similar electrical resistance drop behavior of more than 3 orders of magnitude in La$_{2}$NiO$_{4+\delta}$. However, our extensive investigations reveal that this phenomenon is a novel insulator-to-metal transition, distinct from superconductivity. Intriguingly, compared to the weak magnetic-field effects, pressure can significantly suppress the transition and transform from the metallic to an insulating ground state, accompanied by an isostructural phase transition. Our work not only elucidates the fundamental properties of the metallic conducting ground state in La$_{2}$NiO$_{4+\delta}$, but also critically challenges the notion of superconductivity in single-layer lanthanum nickelates.

The locally noncentrosymmetric heavy fermion superconductor CeRh$_{2}$As$_{2}$ has attracted considerable interests due to its rich superconducting phases, accompanied by possible quadrupole density wave and pronounced antiferromagnetic excitations. To understand the underlying physics, here we report measurements from high-resolution angle-resolved photoemission. Our results reveal fine splittings of the conduction bands related to the locally noncentrosymmetric structure, as well as a quasi-two-dimensional Fermi surface (FS) with strong $4f$ contributions. The FS shows signs of nesting with an in-plane vector ${\boldsymbol q}_1 = (\pi/a$, $\pi/a$), which is facilitated by the heavy bands near $\bar{X}$ arising from the characteristic conduction-$f$ hybridization. The FS nesting provides a natural explanation for the observed antiferromagnetic spin fluctuations at ($\pi/a$, $\pi/a$), which might be the driving force for its unconventional superconductivity. Our experimental results can be reasonably explained by density functional theory plus dynamical mean field theory calculations, which can capture the strong correlation effects. Our study not only provides spectroscopic signature of the key factors underlying the field-induced superconducting transition, but also uncovers the critical role of FS nesting and lattice Kondo effect in the underlying magnetic fluctuations.

Manipulating magnetic domain structure plays a key role in advanced spintronics devices. Theoretical rationale is that the labyrinthine domain structure, normally appearing in ferromagnetic thin films with strong magnetic anisotropy, shows a great potential to increase data storage density for designing magnetic nonvolatile memory and logic devices. However, an electrical control of labyrinthine domain structure remains elusive. Here, we demonstrate the gate-driven evolution of labyrinthine domain structures in an itinerant ferromagnet Cr$_{{7}}$Te$_{{8}}$. By combining electric transport measurements and micromagnetic finite difference simulations, we find that the hysteresis loop of anomalous Hall effect in Cr$_{{7}}$Te$_{{8}}$ samples shows distinct features corresponding to the generation of labyrinthine domain structures. The labyrinthine domain structures are found to be electrically tunable via Li-electrolyte gating, and such gate-driven evolution in Cr$_{{7}}$Te$_{{8}}$ originates from the reduction of the magnetic anisotropic energy with gating, revealed by our micromagnetic simulations. Our results on the gate control of anomalous Hall effect in an itinerant magnetic material provide an opportunity to understand the formation and evolution of labyrinthine domain structures, paving a new route towards electric-field driven spintronics.

By using muon spin relaxation (µSR) measurements, we perform a comparative study of the microscopic magnetism in the parent compounds of infinite-layer nickelate superconductors $R$NiO$_{2}$ ($R$ = La, Nd). In either compound, the zero-field µSR spectra down to the lowest measured temperature reveal no long-range magnetic order. In LaNiO$_{2}$, short-range spin correlations appear below $T=150$ K, and spins fully freeze below $T \sim 10$ K. NdNiO$_{2}$ exhibits a more complex spin dynamics driven by the Nd $4f$ and Ni $3d$ electron spin fluctuations. Further, it shows features suggesting the proximity to a spin-glass state occurring below $T=5$ K. In both compounds, the spin behavior with temperature is further confirmed by longitudinal-field µSR measurements. These results provide new insight into the magnetism of the parent compounds of the superconducting nickelates, crucial to understanding the microscopic origin of their superconductivity.

After the discovery of the ARECh$_{2}$ (A = alkali or monovalent ions, RE = rare-earth, Ch = chalcogen) triangular lattice quantum spin liquid (QSL) family, a series of its oxide, sulfide, and selenide counterparts has been consistently reported and extensively investigated. While KErTe$_{2}$ represents the initial synthesized telluride member, preserving its triangular spin lattice, it was anticipated that the substantial tellurium ions could impart more pronounced magnetic attributes and electronic structures to this material class. This study delves into the magnetism of KErTe$_{2}$ at finite temperatures through magnetization and electron spin resonance (ESR) measurements. Based on the angular momentum $\hat{J}$ after spin-orbit coupling (SOC) and symmetry analysis, we obtain the magnetic effective Hamiltonian to describe the magnetism of Er$^{3+}$ in $R\bar{3}m$ space group. Applying the mean-field approximation to the Hamiltonian, we can simulate the magnetization and magnetic heat capacity of KErTe$_{2}$ in paramagnetic state and determine the crystalline electric field (CEF) parameters and partial exchange interactions. The relatively narrow energy gaps between the CEF ground state and excited states exert a significant influence on the magnetism. For example, small CEF excitations can result in a significant broadening of the ESR linewidth at 2 K. For the fitted exchange interactions, although the values are small, given a large angular momentum $J=15/2$ after SOC, they still have a noticeable effect at finite temperatures. Notably, the heat capacity data under different magnetic fields along the $c$ axis direction also roughly match our calculated results, further validating the reliability of our analytical approach. These derived parameters serve as crucial tools for future investigations into the ground state magnetism of KErTe$_{2}$. The findings presented herein lay a foundation for exploration of the intricate magnetism within the triangular-lattice delafossite family.

With the increasing demand for high-resolution x-ray tomography in battery characterization, the challenges of storing, transmitting, and analyzing substantial imaging data necessitate more efficient solutions. Traditional data compression methods struggle to balance reduction ratio and image quality, often failing to preserve critical details for accurate analysis. This study proposes a machine learning-assisted compression method tailored for battery x-ray imaging data. Leveraging physics-informed representation learning, our approach significantly reduces file sizes without sacrificing meaningful information. We validate the method on typical battery materials and different x-ray imaging techniques, demonstrating its effectiveness in preserving structural and chemical details. Experimental results show an up-to-95 compression ratio while maintaining high fidelity in the projection and reconstructed images. The proposed framework provides a promising solution for managing large-scale battery x-ray imaging datasets, facilitating significant advancements in battery research and development.