Chinese Physics Letters

We employ the Hirota bilinear method to systematically derive nondegenerate bright one- and two-soliton solutions, along with degenerate bright-dark two- and four-soliton solutions for the reverse-time nonlocal nonlinear Schrödinger equation. Beyond the fundamental nondegenerate one-soliton solution, we have identified and characterized nondegenerate breather bound state solitons, with particular emphasis on their evolution dynamics. Furthermore, we have conducted a comprehensive analysis of the dynamic behavior exhibited by degenerate bright-dark soliton structures. These findings offer potential applications for nondegenerate and degenerate soliton interactions in nonlocal models.

Layer pseudospins, exhibiting quantum coherence and precise multistate controllability, present significant potential for the advancement of future computing technologies. In this work, we propose an in-memory probabilistic computing scheme based on the electrical manipulation of layer pseudospins in layered materials, by exploiting the interaction between real spins and layer pseudospins. This approach demonstrates near-linear time complexity, achieving computation speeds approximately five times faster than conventional probabilistic computing schemes for the Maximum Cut (MAXCUT) optimization problem. Moreover, we demonstrate that our proposed scheme can realize a computation speed comparable to quantum computing when the MAXCUT problem with a large number of nodes is considered. Our results highlight the potential of layer degree of freedom as a new information carrier for building up advanced computational systems.

Ramsey oscillations typically exhibit an exponential decay envelope due to environmental noise. However, recent experiments have observed nonmonotonic Ramsey fringes characterized by beating patterns, which deviate from the standard behavior. These beating patterns have primarily been attributed to charge-noise fluctuations. In this paper, we have experimentally observed Ramsey fringe with beating pattern for transmon qubits, and traced the origin to electric instruments induced flux noise. We developed a random telegraph noise (RTN) model to simulate the impact of telegraph-like flux-noise sources on Ramsey oscillations. Our simulations demonstrate that strong flux-RTN sources can induce beating patterns in the Ramsey fringes, showing excellent agreement with experimental observations in transmon qubits influenced by electronic environment-induced flux-noise. Our findings provide valuable insights into the role of flux-noise in qubit decoherence and underscore the importance of considering flux-noise RTN when analyzing nonmonotonic Ramsey fringes.

Decays of charmonium into hyperon and antihyperon pairs provide a pristine laboratory for exploring hyperon properties, such as their polarization and decay parameters, and for conducting tests of fundamental symmetries. This brief review highlights the significant progress made in precise tests of CP symmetry at BESIII using entangled hyperon-antihyperon pairs, including $\Lambda \bar{\Lambda }$, $\Sigma \bar{\Sigma }$, $\Xi \bar{\Xi }$, and $\Lambda \bar{\Sigma }$, selected from the high statistics of J/ψ and ψ(3686) events produced in e⁺e⁻ annihilations. These recent findings have sparked renewed interest in both theoretical and experimental aspects of hyperon physics, but there is still much room for improvement to reach the Standard Model expectations. To address this challenge, the prospects for future investigations on CP asymmetry at next-generation experiments are discussed.

Multi-electron and multi-orbital effects play a crucial role in the interaction of strong laser fields with complex molecules. Here, multi-electron effects encompass not only electron-electron Coulomb interactions and exchange-correlation effects but also the interference between the dynamics of different electron wave packets. In this study, we employ time-dependent density functional theory to investigate high-harmonic generation in benzonitrile (C₇H₅N) subjected to intense infrared laser fields. We find that when the laser polarization direction forms a 45-degree angle with the N–C–C–C axis, the HHG signal perpendicular to this axis exhibits a significant enhancement in the 23rd–31st harmonic orders. Our analysis shows that this enhancement does not align with the classical three-step model but instead arises purely from quantum interference between different orbital channels. Our study reveals that multiple inner-shell orbitals and multi-electron effects play a crucial role in shaping this harmonic spectrum. These findings provide deeper insights into HHG mechanisms and contribute to advancements in strong-field physics and attosecond science.

The quantum metric manifested as the Riemannian metric in the parameter space of Bloch bands, characterizes the topology and geometry of quantum states. The second harmonic generation (SHG), as one of the fundamental nonlinear optical responses that links geometry of optical transitions to physical observables, despite being widely studied in various materials, its relation to quantum metric, especially in the dynamical regime, stays obscure. Here, we investigate the SHG within the Keldysh formalism and resolve the contributions from quantum metric. Using a Haldane model, we simulate the dynamic photocurrent, revealing a significant enhancement of SHG in the transparent region, i.e., for below-gap photon energies. Further, we show that such enhancement originates from the non-Hermitian nature of its complex band structure and quantum tunneling near the exceptional points. Such low-energy-photon SHG signals are highly sensitive to the topological phase transition, quantifying the quantum volume effect. Our work elucidates the physical origin of quantum metric contributed SHG and its relation with topology, providing an alternative route to probe the ultrafast topological phase transition in magnetic insulators.

An accurate and simultaneous ab initio prediction for both light nuclei and nuclear matter has been a long-standing challenge in nuclear physics, due to the significant uncertainties associated with the three-nucleon forces. In this Letter, we develop the relativistic quantum Monte Carlo methods for the nuclear ab initio problem, and calculate the ground-state energies of A ≤ 4 nuclei using the two-nucleon Bonn force with an unprecedented high accuracy. The present relativistic results significantly outperform the nonrelativistic results with only two-nucleon forces. We demonstrate that both light nuclei and nuclear matter can be well described simultaneously in the relativistic ab initio calculations, even in the absence of three-nucleon forces, and a correlation between the properties of light A ≤ 4 nuclei and the nuclear saturation is revealed. This provides a quantitative understanding of the connection between the light nuclei and nuclear matter saturation properties.

By extending the concept of diffusion to the potential energy landscapes (PELs), we introduce the mean-squared energy difference (MSED) as a novel quantity to investigate the intrinsic properties of supercooled liquids. MSED can provide a clear description of the "energy relaxation" process on a PEL. Through MSED analysis, we have obtained a characteristic time similar to that derived from structure analysis, namely ${\tau }_{\alpha }^{\ast }$. Further, we establish a connection between MSED and the feature of PELs, providing a concise and quantitative description of PELs. The relaxation behavior of energy has been found to follow a stretched exponential form. As the temperature decreases, the roughness of the accessible PEL changes significantly around a characteristic temperature T_x, which is 20% higher than the glass transition temperature T_g and is comparable to the critical temperature of the mode-coupling theory. More importantly, one of the PEL parameters is closely related to the Adam–Gibbs configurational entropy. The present research, which directly links the PEL to the relaxation process, provides avenues for further research of glasses.

The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic simulations, we investigate recently synthesized ultrathin perovskite bismuth ferrite (BFO) films. Our numerical results reveal that, at the monolayer limit, the ferroelectricity of BFO is missing because the octahedral distortions are constrained. However, the monolayer bismuth ferrite is a topological antiferromagnetic metal with tunable bimeron magnetic structure. The dual topologically non-trivial characteristics make monolayer bismuth ferrite a multifunctional building block in future spintronic devices.

High-dimensional (HD) entanglement of photonic orbital angular momentum (OAM) is pivotal for advancing quantum communication and information processing, but its characterization remains significant challenges due to the complexity of quantum state tomography and experimental limitations such as low photon counts caused by losses. Here, we propose a pre-trained physics-informed neural network (PTPINN) framework that enables efficient and rapid reconstruction of HD-OAM entangled states under low photon counts. Experimental results show that the fidelity of five-dimensional OAM entanglement reaches F = 0.958 ± 0.010 even with an exposure time as short as 50 ms. This highlights the capability of PTPINN to achieve high-precision quantum state reconstruction with limited photons, owing to its innovative designs, thus overcoming the reliance on high photon counts typical of traditional methods. Our method provides a practical and scalable solution for high-fidelity characterization of HD-OAM entanglement in environments with low photon numbers and high noise, paving the way for robust long-distance quantum information transmission.

Decays of charmonium into hyperon and antihyperon pairs provide a pristine laboratory for exploring hyperon properties, such as their polarization and decay parameters, and for conducting tests of fundamental symmetries. This brief review highlights the significant progress made in precise tests of CP symmetry at BESIII using entangled hyperon-antihyperon pairs, including $\Lambda \bar{\Lambda }$, $\Sigma \bar{\Sigma }$, $\Xi \bar{\Xi }$, and $\Lambda \bar{\Sigma }$, selected from the high statistics of J/ψ and ψ(3686) events produced in e⁺e⁻ annihilations. These recent findings have sparked renewed interest in both theoretical and experimental aspects of hyperon physics, but there is still much room for improvement to reach the Standard Model expectations. To address this challenge, the prospects for future investigations on CP asymmetry at next-generation experiments are discussed.

Quantum integrability provides a unique and powerful framework for accurately understanding quantum magnetism. In this review, we focus specifically on several quantum integrable low-dimensional quantum Ising models. We begin with the transverse field Ising chain (TFIC) at quantum critical point and examine how it evolves under perturbations, such as an applied longitudinal field or weak coupling to another quantum critical TFIC. These perturbations reveal a wealth of emergent quantum integrable field theories with exotic many-body excitations, elegantly characterized by conformal invariance and the E₈ and ${D}_{8}^{(1)}$ Lie algebras, respectively. In exploring these models, we also delve into the framework of exact scattering matrices, which is related to determining spin dynamics within these systems. Finally, we show how the emergent phenomena in these integrable quantum Ising models find experimental realization in Co-based quasi-one-dimensional quantum magnetic materials. The substantial theoretical and experimental advancements in these systems highlight the profound connections between quantum integrable field theory, statistical field theory, and condensed matter physics.

Deconfined quantum critical points (DQCPs) have been proposed as a class of continuous quantum phase transitions occurring between two ordered phases with distinct symmetry-breaking patterns, beyond the conventional framework of Landau-Ginzburg-Wilson (LGW) theory. At the DQCP, the system exhibits emergent gauge fields, fractionalized excitations, and enhanced symmetries. Here we review recent theoretical and experimental progress on exploring DQCPs in condensed matter systems. We first introduce theoretical advancements in the study of DQCPs over the past twenty years, particularly in magnetic models on square lattices, honeycomb lattices, kagome lattices, and one-dimensional spin chains. We then discuss recent progress on experimental realization of DQCP in quantum magnetic systems. Experimentally, the Shastry-Sutherland model, realized in SrCu₂(BO₃)₂, offers a particularly promising platform for realizing DQCPs. The magnetic frustration inherent to this model drives phase transitions between two distinct symmetry-breaking states: a valence bond solid (VBS) phase and a Néel antiferromagnetic phase. Remarkably, SrCu₂(BO₃)₂ has provided the first experimental evidence of a proximate DQCP through a field-induced Bose-Einstein condensation, transitioning from the VBS state to the Néel state. Nevertheless, the direct experimental realization of a DQCP remains a significant challenge. Despite this, it offers a promising platform for exploring emergent phenomena through quantum phase transition in low-dimensional quantum systems.

The Kitaev honeycomb model has received significant attention due to its exactly solvable quantum spin liquid ground states and fractionalized excitations. Layered cobalt oxides have been considered as a promising platform for realizing this model. However, in contrast to the conventional wisdom regarding the single-q zigzag magnetic order inferred from previous studies of the candidate materials Na₂IrO₃ and α-RuCl₃, recent experiments on two representative honeycomb cobalt oxides, hexagonal Na₂Co₂TeO₆ and monoclinic Na₃Co₂SbO₆, have uncovered evidence for more complex multi-q zigzag order variants. This review surveys the experimental strategies used to distinguish between single- and multi-q orders, along with the crystallographic symmetries of cobalt oxides, in comparison with previously studied systems. The general formation mechanism of multi-q order is also briefly discussed. The goal is to provide a solid ground for examining the relevance of multi-q order in honeycomb cobalt oxides and discuss its implications for the microscopic model of these intriguing quantum magnets.

The discovery of advanced materials is a cornerstone of human technological development and progress. The structures of materials and their corresponding properties are essentially the result of a complex interplay of multiple degrees of freedom such as lattice, charge, spin, symmetry, and topology. This poses significant challenges for the inverse design methods of materials. Humans have long explored new materials through numerous experiments and proposed corresponding theoretical systems to predict new material properties and structures. With the improvement of computational power, researchers have gradually developed various electronic-structure calculation methods, such as the density functional theory and high-throughput computational methods. Recently, the rapid development of artificial intelligence (AI) technology in computer science has enabled the effective characterization of the implicit association between material properties and structures, thus forming an efficient paradigm for the inverse design of functional materials. Significant progress has been achieved in the inverse design of materials based on generative and discriminative models, attracting widespread interest from researchers. Considering this rapid technological progress, in this survey, we examine the latest advancements in AI-driven inverse design of materials by introducing the background, key findings, and mainstream technological development routes. In addition, we summarize the remaining challenges for future directions. This survey provides the latest overview of AI-driven inverse design of materials, which can serve as a useful resource for researchers.

This paper explores the rich structure of peakon and pseudo-peakon solutions for a class of higherorder b-family equations, referred to as the J-th b-family (J-bF) equations. We propose several conjectures concerning the weak solutions of these equations, including a b-independent pseudopeakon solution, a b-independent peakon solution, and a b-dependent peakon solution. These conjectures are analytically verified for J ≤ 14 and/or J ≤ 9 using the symbolic computation system MAPLE, which includes a built-in definition of the higher-order derivatives of the sign function. The b-independent pseudo-peakon solution is a 3rd-order pseudo-peakon for general arbitrary constants, with higher-order pseudo-peakons derived under specific parameter constraints. Additionally, we identify both b-independent and b-dependent peakon solutions, highlighting their distinct properties and the nuanced relationship between the parameters b and J. The existence of these solutions underscores the rich dynamical structure of the J-bF equations and generalizes previous results for lower-order equations. Future research directions include higher-order generalizations, rigorous proofs of the conjectures, interactions between different types of peakons and pseudo-peakons, stability analysis, and potential physical applications. These advancements significantly contribute to the understanding of peakon systems and their broader implications in mathematics and physics.

The recent discovery of superconductivity in La₃Ni₂O_7-δ with a transition temperature Tc close to 80 K at high pressures has attracted significant attention, due particularly to a possible density wave (DW) transition occurring near the superconducting dome. Identifying the type of DW order is crucial for understanding the origin of superconductivity in this system. However, owing to the presence of La₄Ni₃O₁₀ and other intergrowth phases in La₃Ni₂O_7-δ samples, extracting the intrinsic information from the La₃Ni₂O₇ phase is challenging. In this study, we employed ¹³⁹La nuclear quadrupole resonance (NQR) measurements to eliminate the influence of other structural phases in the sample and obtain microscopic insights into the DW transition in La₃Ni₂O_7-δ. Below the DW transition temperature T^DW ~ 153K, we observe a distinct splitting in the ± 5/2 ↔ ± 7/2 transition of the NQR resonance peak at the La(2) site, while only a line broadening is seen in the ± 3/2 ↔ ± 5/2 transition peak. Through further analysis of the spectra, we show that the line splitting is due to a unidirectional charge modulation. A magnetic line broadening is also observed below TDW, accompanied by a large enhancement of the spin-lattice relaxation rate, indicating the formation of magnetically ordered moments in the DW state. Our results suggest a simultaneous formation of chargeand spin-density wave order in La₃Ni₂O_7-δ, thereby offering critical insights into the electronic correlations in Ni-based superconductors.

Altermagnets represent a newly discovered class of magnetically ordered materials. Among all the candidates, CrSb stands out due to its largest spin splitting energy and highest Nel temperature exceeding 700 K, making it promising for room-temperature spintronic applications. Here we have successfully grown high quality CrSb (100) thin film on GaAs (110) substrate by molecular beam epitaxy. Using angle-resolved photoemission spectroscopy, we successfully obtained the threedimensional electronic structure of the thin film. Moreover, we observed the emergence of the altermagnetic splitting bands corresponding to the calculated results along the low symmetry paths T-Q and P-D. The bands near the Fermi level are only spin splitting bands along the P-D direction, with splitting energy reaching as high as 910 meV. This finding provides insights into the magnetic properties of CrSb thin films and paves the way for further studies on their electronic structure and potential applications in spintronics.

Scalar field should have no spin angular momentum according to conventional textbook understandings in classical field theory. Yet, recent studies demonstrate the undoubted existence of wave spin endowed by acoustic and elastic longitudinal waves, which are of irrotational curl-free nature without vorticity and can be described by scalar fields. Moreover, the conventional theory can not even answer the question of whether wave spin exists in dissipative fields, given the ubiquitous dissipation in reality. Here, to resolve the seeming paradox and answer the challenging question, we uncover the origin of wave spin in scalar fields beyond traditional formalism by clarifying that the presence of higher order derivatives in scalar field Lagrangians can give rise to non-vanishing wave spin. For "spinless" scalar fields of only first order derivative, we can make the hidden wave spin emerge, by revealing a latent field that leads to the original field through a time derivative so that giving higher order terms in Lagrangian. Based on the standard Noether theorem approach, we exemplify the wave spin for unconventional drifted acoustic fields, and even for dissipative media, in scalar fields with higherorder derivative Lagrangian. The results would prompt people to build more comprehensive and fundamental understandings of structural wave spin in classical fields.

Anti-phase domain defects easily form in the in-plane GaAs NWs grown on CMOS-compatible group IV substrates, which makes it difficult to obtain GaAs NWs with a designed length and also leads to a significant limitation in the growth of highquality in-plane GaAs NW networks on such substrates. Here, we report on the selective area growth of anti-phase domain free in-plane GaAs NWs and NW networks on Ge (111) substrates. Detailed structural studies confirm that the GaAs NW grown using a large pattern period and GaAs NW networks grown by adding the Sb both are highquality pure zinc-blende single crystals free of stacking faults, twin defects and antiphase domain defects. Room-temperature photoluminescence measurements show a substantial improvement in crystal quality and good consistency and uniformity of the GaAs NW networks. Our work provides useful insights into the controlled growth of high-quality anti-phase domain defects free in-plane III-V NWs and NW networks.