Motivated by the recent discovery of high-temperature superconductivity in bilayer La$_3$Ni$_2$O$_7$ under pressure, we study its electronic properties and superconductivity due to strong electron correlation. Using the inversion symmetry, we decouple the low-energy electronic structure into block-diagonal symmetric and antisymmetric sectors. It is found that the antisymmetric sector can be reduced to a one-band system near half filling, while the symmetric bands occupied by about two electrons are heavily overdoped individually. Using the strong coupling mean field theory, we obtain strong superconducting pairing with $B_{\rm 1g}$ symmetry in the antisymmetric sector. We propose that due to the spin-orbital exchange coupling between the two sectors, $B_{\rm 1g}$ pairing is induced in the symmetric bands, which in turn boosts the pairing gap in the antisymmetric band and enhances the high-temperature superconductivity with a congruent d-wave symmetry in pressurized La$_3$Ni$_2$O$_7$.

Within the extended vector meson dominance model, we investigate the $e^+ e^- \to \varLambda^+_c \bar{\varLambda}^-_c$ reaction and the electromagnetic form factors of the charmed baryon $\varLambda_c^+$. The model parameters are determined by fitting them to the cross sections of the process $e^+e^-\rightarrow \varLambda_c^+ \bar{\varLambda}_c^-$ and the magnetic form factor $|G_{\scriptscriptstyle{\rm M}}|$ of $\varLambda^+_c$. By considering four charmonium-like states, called $\psi(4500)$, $\psi(4660)$, $\psi(4790)$, and $\psi(4900)$, we can well describe the current data on the $e^+ e^- \to \varLambda^+_c \bar{\varLambda}^-_c$ reaction from the reaction threshold up to $4.96$ GeV. In addition to the total cross sections and $|G_{\scriptscriptstyle{\rm M}}|$, the ratio $|G_{\scriptscriptstyle{\rm E}}/G_{\scriptscriptstyle{\rm M}}|$ and the effective form factor $|G_{\mathrm{eff}}|$ for $\varLambda^+_c$ are also calculated, and found that these calculations are consistent with the experimental data. Within the fitted model parameters, we have also estimated the charge radius of the charmed $\varLambda_c^+$ baryon.

Moiré superlattices in twisted two-dimensional materials have emerged as ideal platforms for engineering quantum phenomena, which are highly sensitive to twist angles, including both the global value and the spatial inhomogeneity. However, only a few methods provide spatial-resolved information for characterizing local twist angle distribution. Here we directly visualize the variations of local twist angles and angle-dependent evolutions of the quantum states in twisted bilayer graphene by scanning microwave impedance microscopy (sMIM). Spatially resolved sMIM measurements reveal a pronounced alteration in the local twist angle, approximately 0.3$^{\circ}$ over several micrometers in some cases. The variation occurs not only when crossing domain boundaries but also occasionally within individual domains. Additionally, the full-filling density of the flat band experiences a change of over $2 \times 10^{11}$ cm$^{-2}$ when crossing domain boundaries, aligning consistently with the twist angle inhomogeneity. Moreover, the correlated Chern insulators undergo variations in accordance with the twist angle, gradually weakening and eventually disappearing as the deviation from the magic angle increases. Our findings signify the crucial role of twist angles in shaping the distribution and existence of quantum states, establishing a foundational cornerstone for advancing the study of twisted two-dimensional materials.

Surface acoustic wave (SAW) is a powerful technique for investigating quantum phases appearing in two-dimensional electron systems. The electrons respond to the piezoelectric field of SAW through screening, attenuating its amplitude, and shifting its velocity, which is described by the relaxation model. In this work, we systematically study this interaction using orders of magnitude lower SAW amplitude than those in previous studies. At high magnetic fields, when electrons form highly correlated states such as the quantum Hall effect, we observe an anomalously large attenuation of SAW, while the acoustic speed remains considerably high, inconsistent with the conventional relaxation model. This anomaly exists only when the SAW power is sufficiently low.

The discovery of high-temperature superconductivity near 80 K in bilayer nickelate La$_{3}$Ni$_{2}$O$_{7}$ under high pressures has renewed the exploration of superconducting nickelate in bulk materials. The extension of superconductivity in other nickelates in a broader family is also essential. Here, we report the experimental observation of superconducting signature in trilayer nickelate La$_{4}$Ni$_{3}$O$_{10}$ under high pressures. By using a modified sol-gel method and post-annealing treatment under high oxygen pressure, we successfully obtained polycrystalline La$_{4}$Ni$_{3}$O$_{10}$ samples with different transport behaviors at ambient pressure. Then we performed high-pressure electrical resistance measurements on these samples in a diamond-anvil-cell apparatus. Surprisingly, the signature of possible superconducting transition with a maximum transition temperature ($T_{\rm c}$) of about 20 K under high pressures is observed, as evidenced by a clear drop of resistance and the suppression of resistance drops under magnetic fields. Although the resistance drop is sample-dependent and relatively small, it appears in all of our measured samples. We argue that the observed superconducting signal is most likely to originate from the main phase of La$_{4}$Ni$_{3}$O$_{10}$. Our findings will motivate the exploration of superconductivity in a broader family of nickelates and shed light on the understanding of the underlying mechanisms of high-$T_{\rm c}$ superconductivity in nickelates.

Semiconductor devices are often operated at elevated temperatures that are well above zero Kelvin, which is the temperature in most first-principles density functional calculations. Computational approaches to computing and understanding the properties of semiconductors at finite temperatures are thus in critical demand. In this review, we discuss the recent progress in computationally assessing the electronic and phononic band structures of semiconductors at finite temperatures. As an emerging semiconductor with particularly strong temperature-induced renormalization of the electronic and phononic band structures, halide perovskites are used as a representative example to demonstrate how computational advances may help to understand the band structures at elevated temperatures. Finally, we briefly illustrate the remaining computational challenges and outlook promising research directions that may help to guide future research in this field.

Quantum excitation is usually regarded as a transient process occurring instantaneously, leaving the underlying physics shrouded in mystery. Recent research shows that Rydberg-state excitation with ultrashort laser pulses can be investigated and manipulated with state-of-the-art few-cycle pulses. We theoretically find that the efficiency of Rydberg state excitation can be enhanced with a short laser pulse and modulated by varying the laser intensities. We also uncover new facets of the excitation dynamics, including the launching of an electron wave packet through strong-field ionization, the re-entry of the electron into the atomic potential and the crucial step where the electron makes a U-turn, resulting in twin captures into Rydberg orbitals. By tuning the laser intensity, we show that the excitation of the Rydberg state can be coherently controlled on a sub-optical-cycle timescale. Our work paves the way toward ultrafast control and coherent manipulation of Rydberg states, thus benefiting Rydberg-state-based quantum technology.

We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.

This concise review summarizes recent advancements in theoretical studies of vortex quantum droplets (VQDs) in matter-wave fields. These are robust self-trapped vortical states in two- and three-dimensional (2D and 3D) Bose–Einstein condensates (BECs) with intrinsic nonlinearity. Stability of VQDs is provided by additional nonlinearities resulting from quantum fluctuations around mean-field states, often referred to as the Lee–Huang–Yang (LHY) corrections. The basic models are presented, with emphasis on the interplay between the mean-field nonlinearity, LHY correction, and spatial dimension, which determines the structure and stability of VQDs. We embark by delineating fundamental properties of VQDs in the 3D free space, followed by consideration of their counterparts in the 2D setting. Additionally, we address stabilization of matter-wave VQDs by optical potentials. Finally, we summarize results for the study of VQDs in the single-component BEC of atoms carrying magnetic moments. In that case, the anisotropy of the long-range dipole-dipole interactions endows the VQDs with unique characteristics. The results produced by the theoretical studies in this area directly propose experiments for the observation of novel physical effects in the realm of quantum matter, and suggest potential applications to the design of new schemes for processing classical and quantum information.

We report a linear-scaling random Green's function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H$_{2}$O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H$_{2}$O clusters at $T=0$ K can reach an error of $\sim$ $1$ meV per H$_{2}$O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.

While density functional theory (DFT) serves as a prevalent computational approach in electronic structure calculations, its computational demands and scalability limitations persist. Recently, leveraging neural networks to parameterize the Kohn–Sham DFT Hamiltonian has emerged as a promising avenue for accelerating electronic structure computations. Despite advancements, challenges such as the necessity for computing extensive DFT training data to explore each new system and the complexity of establishing accurate machine learning models for multi-elemental materials still exist. Addressing these hurdles, this study introduces a universal electronic Hamiltonian model trained on Hamiltonian matrices obtained from first-principles DFT calculations of nearly all crystal structures on the Materials Project. We demonstrate its generality in predicting electronic structures across the whole periodic table, including complex multi-elemental systems, solid-state electrolytes, Moiré twisted bilayer heterostructure, and metal-organic frameworks. Moreover, we utilize the universal model to conduct high-throughput calculations of electronic structures for crystals in GNoME datasets, identifying 3940 crystals with direct band gaps and 5109 crystals with flat bands. By offering a reliable efficient framework for computing electronic properties, this universal Hamiltonian model lays the groundwork for advancements in diverse fields, such as easily providing a huge data set of electronic structures and also making the materials design across the whole periodic table possible.

High-order quantum coherence reveals the statistical correlation of quantum particles. Manipulation of quantum coherence of light in the temporal domain enables the production of the single-photon source, which has become one of the most important quantum resources. High-order quantum coherence in the spatial domain plays a crucial role in a variety of applications, such as quantum imaging, holography, and microscopy. However, the active control of second-order spatial quantum coherence remains a challenging task. Here we predict theoretically and demonstrate experimentally the first active manipulation of second-order spatial quantum coherence, which exhibits the capability of switching between bunching and anti-bunching, by mapping the entanglement of spatially structured photons. We also show that signal processing based on quantum coherence exhibits robust resistance to intensity disturbance. Our findings not only enhance existing applications but also pave the way for broader utilization of higher-order spatial quantum coherence.

SnO$_{2}$ films exhibit significant potential as cost-effective and high electron mobility substitutes for In$_{2}$O$_{3}$ films. In this study, Li is incorporated into the interstitial site of the SnO$_{2}$ lattice resulting in an exceptionally low resistivity of $2.028 \times 10^{-3}\,\Omega \cdot$cm along with a high carrier concentration of $1.398 \times 10^{20}$ cm$^{-3}$ and carrier mobility of 22.02 cm$^{2}$/V$\cdot$s. Intriguingly, Li$_{i}$ readily forms in amorphous structures but faces challenges in crystalline formations. Furthermore, it has been experimentally confirmed that Li$_{i}$ acts as a shallow donor in SnO$_{2}$ with an ionization energy $\Delta E_{\rm D1}$ of $-0.4$ eV, indicating spontaneous occurrence of Li$_{i}$ ionization.

We investigate the nature of the strong coupling constant and related physics. Through the analysis of accumulated experimental data around the world, we employ the ability of machine learning to unravel its physical laws. The result of our efforts is a formula that captures the expansive panorama of the distribution of the strong coupling constant across the entire energy range. Importantly, this newly derived expression is very similar to the formula derived from the Dyson–Schwinger equations based on the framework of Yang–Mills theory. By introducing the Euler number $e$ into the functional formula of the strong coupling constant at high energies, we successfully solve the puzzle of the infrared divergence, which allows for a seamless transition of the strong coupling constant from the perturbative to the non-perturbative energy regime. Moreover, the obtained ghost and gluon dressing function distribution results confirm that the obtained strong coupling constant formula can well describe the physical properties of the non-perturbed regime. In addition, we study the quantum-chromodynamics strong coupling constant result of the Bjorken sum rule $\varGamma_1^{p-n}$ and the quark–quark static energy $E_0(r)$, and find that the global energy scale can effectively interpret the experimental data. The present results shed light on the puzzling properties of quantum chromodynamics and the intricate interplay of strong coupling constants at both low and high energy scales.

Adiabatic time-optimal quantum controls are extensively used in quantum technologies to break the constraints imposed by short coherence times. However, practically it is crucial to consider the trade-off between the quantum evolution speed and instantaneous energy cost of process because of the constraints in the available control Hamiltonian. Here, we experimentally show that using a transmon qubit that, even in the presence of vanishing energy gaps, it is possible to reach a highly time-optimal adiabatic quantum driving at low energy cost in the whole evolution process. This validates the recently derived general solution of the quantum Zermelo navigation problem, paving the way for energy-efficient quantum control which is usually overlooked in conventional speed-up schemes, including the well-known counter-diabatic driving. By designing the control Hamiltonian based on the quantum speed limit bound quantified by the changing rate of phase in the interaction picture, we reveal the relationship between the quantum speed limit and instantaneous energy cost. Consequently, we demonstrate fast and high-fidelity quantum adiabatic processes by employing energy-efficient driving strengths, indicating a promising strategy for expanding the applications of time-optimal quantum controls in superconducting quantum circuits.

We propose a simple quantum voting machine using microwave photon qubit encoding, based on a setup comprising multiple microwave cavities and a coupled superconducting flux qutrit. This approach primarily relies on a multi-control single-target quantum phase gate. The scheme offers operational simplicity, requiring only a single step, while ensuring verifiability through the measurement of a single qubit phase information to obtain the voting results. It provides voter anonymity, as the voting outcome is solely tied to the total number of affirmative votes. Our quantum voting machine also has scalability in terms of the number of voters. Additionally, the physical realization of the quantum voting machine is general and not limited to circuit quantum electrodynamics. Quantum voting machine can be implemented as long as the multi-control single-phase quantum phase gate is realized in other physical systems. Numerical simulations indicate the feasibility of this quantum voting machine within the current quantum technology.

We propose a quasi-one-dimensional non-Hermitian Creutz ladder with an entirely flat spectrum by introducing alternating gain and loss components while maintaining inversion symmetry. Destructive interference generates a flat spectrum at the exceptional point, where the Creutz ladder maintains coalesced and degenerate eigenvalues with compact localized states distributed in a single plaquette. All excitations are completely confined within the localization area, unaffected by gain and loss. Single-site excitations exhibit nonunitary dynamics with intensities increasing due to level coalescence, while multiple-site excitations may display oscillating or constant intensities at the exceptional point. These results provide insights into the fascinating dynamics of non-Hermitian localization, where level coalescence and degeneracy coexist at the exceptional point.

Two-dimensional (2D) magnetic materials have been demonstrated to have excellent chemical, optical, electrical, and magnetic properties, particularly in the development of multifunctional electronic and spin electronic devices, showcasing tremendous potential. Therefore, corresponding synthesis techniques for 2D magnetic materials that offer high quality, high yield, low cost, time-saving, and simplicity are highly desired. This review provides a comprehensive overview of recent research advances in preparation of magnetic 2D materials, with a particular focus on the preparation methods employed. Moreover, the characteristics and applications of these magnetic materials are also discussed. Finally, the challenges and prospects of synthesis methods for magnetic 2D materials are briefly addressed. This review serves as a guiding reference for the controlled synthesis of 2D magnetic materials.

We report the results of a search for radio pulsars in five supernova remnants (SNRs) with the FAST telescope. The observations were made using the 19-beam receiver in “snapshot” mode. The integration time for each pointing was 10 min. We discovered a new pulsar, PSR J1845–0306, which has a spin period of 983.6 ms and a dispersion measure of 444.6 $\pm$ 2.0 cm$^{-3}$$\cdot$pc, in observations of SNR G29.6+0.1. To judge the association between the pulsar and the SNR, further verification is needed. We also re-detected some known pulsars in the data from SNRs G29.6+0.1 and G29.7–0.3. No pulsars were detected in the observations of the other three SNRs.

Quantum gates are crucial for quantum computation and quantum information processing. However, their effectiveness is often hindered by systematic errors and decoherence. Therefore, achieving resilient quantum gates to these factors is of great significance. We present a method to construct nonadiabatic holonomic single- and two-qubit gates in a Rydberg ground-state-blockade regime. Our approach utilizes a far-off-resonant technique for the single-qubit gate and a modified Rydberg antiblockade for the two-qubit gate. The reduction of the population of single- and two-excitation Rydberg states and the nonadiabatic holonomic process during the construction of the gates ensure robustness to decoherence and systematic errors, respectively. Numerical results demonstrate the fidelity and robustness of our scheme. The proposed scheme holds promise for future applications in quantum computation and quantum information processing tasks.

Semiconductor nanowires coupled to a superconductor provide a powerful testbed for quantum device physics such as Majorana zero modes and gate-tunable hybrid qubits. The performance of these quantum devices heavily relies on the quality of the induced superconducting gap. A hard gap, evident as vanishing subgap conductance in tunneling spectroscopy, is both necessary and desired. A hard gap has been achieved and extensively studied before in III–V semiconductor nanowires (InAs and InSb). In this study, we present the observation of a hard superconducting gap in PbTe nanowires coupled to a superconductor Pb. The gap size $\varDelta$ is $\sim$ 1 meV (maximally 1.3 meV in one device). Additionally, subgap Andreev bound states can also be created and controlled through gate tuning. Tuning a device into the open regime can reveal Andreev enhancement of the subgap conductance. These results pave the way for diverse superconducting quantum devices based on PbTe nanowires.

Coupling of quantum-dot circuits to microwave photons enables us to investigate photon-assisted quantum transport. Here, we revisit this typical circuit quantum electrodynamical setup by introducing the Kerr nonlinearity of photons. By exploiting quantum critical behavior, we propose a powerful scheme to control the power-harvesting efficiency in the microwave regime, where the driven-dissipative optical system acts as an energy pump. It drives electron transport against a load in the quantum-dot circuit. The energy transfer and, consequently, the harvesting efficiency are enhanced near the critical point. As the critical point moves towards to low input power, high efficiency within experimental parameters is achieved. Our results complement fundamental studies of photon-to-electron conversion at the nanoscale and provide practical guidance for designs of integrated photoelectric devices through quantum criticality.

Controlling the size and distribution of potential barriers within a medium of interacting particles can unveil unique collective behaviors and innovative functionalities. We introduce a unique superconducting hybrid device using a novel artificial spin ice structure composed of asymmetric nanomagnets. This structure forms a distinctive superconducting pinning potential that steers unconventional motion of superconducting vortices, thereby inducing a magnetic nonreciprocal effect, in contrast to the electric nonreciprocal effect commonly observed in superconducting diodes. Furthermore, the polarity of the magnetic nonreciprocity is in situ reversible through the tunable magnetic patterns of artificial spin ice. Our findings demonstrate that artificial spin ice not only precisely modulates superconducting characteristics but also opens the door to novel functionalities, offering a groundbreaking paradigm for superconducting electronics.

A quasi-phase-matched technique is introduced for soliton transmission in a quadratic $[\chi^{(2)}]$ nonlinear crystal to realize the stable transmission of dipole solitons in a one-dimensional space under three-wave mixing. We report four types of solitons as dipole solitons with distances between their bimodal peaks that can be laid out in different stripes. We study three cases of these solitons: spaced three stripes apart, one stripe apart, and confined to the same stripe. For the case of three stripes apart, all four types have stable results, but for the case of one stripe apart, stable solutions can only be found at $\omega_{1}=\omega_{2}$, and for the condition of dipole solitons confined to one stripe, stable solutions exist only for Type1 and Type3 at $\omega_{1}=\omega_{2}$. The stability of the soliton solution is solved and verified using the imaginary time propagation method and real-time transfer propagation, and soliton solutions are shown to exist in the multistability case. In addition, the relations of the transportation characteristics of the dipole soliton and the modulation parameters are numerically investigated. Finally, possible approaches for the experimental realization of the solitons are outlined.

We experimentally and theoretically present a paradigm for the accurate bilayer design of gradient metasurfaces for wave beam manipulation, producing an extremely asymmetric splitting effect by simply tailoring the interlayer size. This concept arises from anomalous diffraction in phase gradient metasurfaces and the precise combination of the phase gradient in bilayer metasurfaces. Ensured by different diffraction routes in momentum space for incident beams from opposite directions, extremely asymmetric acoustic beam splitting can be generated in a robust way, as demonstrated in experiments through a designed bilayer system. Our work provides a novel approach and feasible platform for designing tunable devices to control wave propagation.

We estimate the thermal properties of unsmooth Si nanowires, considering key factors such as size (diameter), surface texture (roughness) and quantum size effects (phonon states) at different temperatures. For nanowires with a diameter of less than 20 nm, we highlight the importance of quantum size effects in heat capacity calculations, using dispersion relations derived from the modified frequency equation for the elasticity of a rod. The thermal conductivities of nanowires with diameters of 37, 56, and 115 nm are predicted using the Fuchs–Sondheimer model and Soffer's specular parameter. Notably, the roughness parameters are chosen to reflect the technological characteristics of the real surfaces. Our findings reveal that surface texture plays a significant role in thermal conductivity, particularly in the realm of ballistic heat transfer within nanowires. This study provides practical recommendations for developing new thermal management materials.

Determination of the magnetic structure and confirmation of the presence or absence of inversion ($\mathcal{P}$) and time reversal ($\mathcal{T}$) symmetry is imperative for correctly understanding the topological magnetic materials. Here high-quality single crystals of the layered manganese pnictide CaMnSb$_2$ are synthesized using the self-flux method. De Haas–van Alphen oscillations indicate a nontrivial Berry phase of $\sim$ $\pi$ and a notably small cyclotron effective mass, supporting the Dirac semimetal nature of CaMnSb$_2$. Neutron diffraction measurements identify a C-type antiferromagnetic structure below $T_{\rm N} = 303(1)$ K with the Mn moments aligned along the $a$ axis, which is well supported by the density functional theory (DFT) calculations. The corresponding magnetic space group is $Pn'm'a'$, preserving a $\mathcal{P}\times\mathcal{T}$ symmetry. Adopting the experimentally determined magnetic structure, band crossings near the $Y$ point in momentum space and linear dispersions of the Sb $5{\rm p}_{y,\,z}$ bands are revealed by the DFT calculations. Furthermore, our study predicts the possible existence of an intrinsic second-order nonlinear Hall effect in CaMnSb$_2$, offering a promising platform to study the impact of topological properties on nonlinear electrical transports in antiferromagnets.

We propose a method to construct Hopf insulators based on the study of topological defects from the geometric perspective of Hopf invariant $I$. Firstly, we prove two types of topological defects naturally inhering in the inner differential structure of the Hopf mapping. One type is the four-dimensional point defects, which lead to a topological phase transition occurring at the Dirac points. The other type is the three-dimensional merons, whose topological charges give the evaluations of $I$. Then, we show two ways to establish the Hopf insulator models. One approach is to modify the locations of merons, thereby the contributions of charges to $I$ will change. The other is related to the number of defects. It is found that $I$ will decrease if the number reduces, while increase if additional defects are added. The method developed in this study is expected to provide a new perspective for understanding the topological invariants, which opens a new door in exploring and designing novel topological materials in three dimensions.

We report a passive mode-locked fiber laser that can realize single-wavelength tuning and multi-wavelength spacing tuning simultaneously. The tuning range is from 1528 nm–1560 nm, and up to three bands of soliton states can be output at the same time. These results are confirmed by a nonlinear Schrödinger equation model based on the split-step Fourier method. In addition, we reveal a way to transform the multi-wavelength soliton state into the Q-switched mode-locked state, which is period doubling. These results will promote the development of optical communication, optical sensing and multi-signal pulse emission.