Multiplicatively introducing the noise and the signal into the gain-noise model of a single-mode laser system, we detect the two forms of stochastic resonance (the single-peak form stochastic resonance and stochastic multiresonance) in the curve of the dependence of signal-to-noise ratio upon the noise correlation time. Moreover, when the correlation coefficient and the intensities of both noises are changed, the two forms of stochastic resonance alternate.

The widths for pionic decays of the lowest two excited doublets (0⁺, 1⁺) and (1⁺, 2⁺) of heavy mesons are studied with quantum Chromodynamics sum rules in the heavy quark effective theory. The interpolating currents used allow us to distinguish the two 1⁺ states without contamination in the infinite mass limit. The soft pion approximation is not used in the calculations.

We report the cumulative reaction probabilities (CRP) of the three-dimensional Cl+H₂ → H+HCl calculated on the Stern-Persky-Klein potential energy surface, using the generalized Newton variational principle, for total angular momentum J =0, over a total reaction energy range from 9 to 19 kcal/mol. The relation between CRP and reaction rate constants, as well as the calculation for complete reaction rates (summed over all J), bypassing the direct calculation of the CRP's for J>0, are also discussed.

Large longitudinal magnetoresistance (LMR) was observed in nonmagnetic silver telluride films. The magnitude of the LMR is not simply dependent on T and H, for example, multi-peaks of ρ at low field and low temperature appear in the Ag-Te film. Because both of -Δρ/ρ and a transition from -Δρ/ρ to +Δρ/ρ exist in Ag-Te films, the magnetoresistance (MR) behavior of the Ag-Te film does not like the bulk Ag-Te, but likes the doped semiconductors. About -27% of LMR was observed at low field in the Ag-Te films, while it could be negligible in the doped semiconductors. The MR behavior in Ag-Te films is discussed by means of a formation of impurity bands in the films.

Strontium titanate films with high a−axis-orientation [a₍₁₀₀₎=94.1%] were deposited on (111) Pt/Ti/SiO₂/Si substrates by the metal organic deposition process. X−ray diffraction shows that the degree of a-axis orientation increases with increasing annealing temperature. It is found that the dielectric properties are improved by a higher annealing temperature, while the leakage currents are also enhanced, and the possible causes of temperature dependence are discussed.

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.

Layer-structured oxides Y_1−xBi_xBaCo₄O₇(0.00 ≤ x ≤ 0.05) were successfully synthesized and their structural and oxygen absorption properties were investigated by x−ray diffraction and thermogravimetry. Though Bi solubility was limited to about 5%, corresponding to Y_0.95Bi_0.05BaCo₄O₇, it is found that the structure and oxygen absorption properties of Y_1−xBi_xBaCo₄O₇ are affected significantly as the Bi content x increases. Rietveld refinement results show that Y_1−xBi_xBaCo₄O₇(x ≤ 0.05) is single phase with a hexagonal crystal structure (space group P6₃mc). Unit cell parameters and volume are changed and CoO₄ tetrahedra are distorted along the c−axis in Bi doped YBaCo₄O₇. The TG results show that Y_1−xBi_xBaCo₄O₇ undergoes two oxygen absorption processes in oxygen from room temperature to 1000°C and the maximum mass increase of the doped samples is less than that of YBaCo₄O₇. Bi doping effects on the structure and oxygen absorption properties are discussed on the basis of average radius and disorder of the Y site, the valence of Bi and the oxygen activation energy.

An intrinsic magnetic topological insulator (TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi$_{2}$Te$_{4}$, by alternate growth of a Bi$_{2}$Te$_{3}$ quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.

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.

Single-layer superconductors are ideal materials for fabricating superconducting nano devices. However, up to date, very few single-layer elemental superconductors have been predicted and especially no one has been successfully synthesized yet. Here, using crystal structure search techniques and ab initio calculations, we predict that a single-layer planar carbon sheet with 4- and 8-membered rings called T-graphene is a new intrinsic elemental superconductor with superconducting critical temperature ($T_{\rm c}$) up to around 20.8 K. More importantly, we propose a synthesis route to obtain such a single-layer T-graphene, that is, a T-graphene potassium intercalation compound (C$_4$K with $P4/mmm$ symmetry) is firstly synthesized at high pressure ($>$11.5 GPa) and then quenched to ambient condition; and finally, the single-layer T-graphene can be either exfoliated using the electrochemical method from the bulk C$_4$K, or peeled off from bulk T-graphite C$_4$, where C$_4$ can be obtained from C$_4$K by evaporating the K atoms. Interestingly, we find that the calculated $T_{\rm c}$ of C$_4$K is about 30.4 K at 0 GPa, which sets a new record for layered carbon-based superconductors. The present findings add a new class of carbon-based superconductors. In particular, once the single-layer T-graphene is synthesized, it can pave the way for fabricating superconducting devices together with other 2D materials using the layer-by-layer growth techniques.

Distribution of the parallel momentum of ²⁸Si fragments from the breakup of 30.7MeV/nucleon ²⁹P has been measured on C targets. The distribution has the FWHM with the value of 110.5±23.5MeV/c, which is quantitatively consistent with the Galuber model calculation assuming by a valence proton in ²⁹P. The density distribution is also predicted by the Skyrme--Hartree--Fock calculation. The results show that the proton-skin structure may exist in ²⁹P.

High-temperature superconductivity (HTSC) remains one of the most challenging and fascinating mysteries in condensed matter physics. Recently, superconductivity with transition temperature exceeding liquid-nitrogen temperature is discovered in La$_{3}$Ni$_{2}$O$_{7}$ at high pressure, which provides a new platform to explore the unconventional HTSC. In this work, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structures of La$_{3}$Ni$_{2}$O$_{7}$ at ambient pressure. Our experiments are in nice agreement with ab initio calculations after considering an orbital-dependent band renormalization effect. The strong electron correlation effect pushes a flat band of $d_{z^{2}}$ orbital component below the Fermi level ($E_{\rm F}$), which is predicted to locate right at $E_{\rm F}$ under high pressure. Moreover, the $d_{x^{2}-y^{2}}$ band shows pseudogap-like behavior with suppressed spectral weight and diminished quasiparticle peak near $E_{\rm F}$. Our findings provide important insights into the electronic structure of La$_{3}$Ni$_{2}$O$_{7}$, which will shed light on understanding of the unconventional superconductivity in nickelates.

High resolution laser-based angle-resolved photoemission measurements are carried out on an overdoped superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ with a $T_{\rm c}$ of 75 K. Two Fermi surface sheets caused by bilayer splitting are clearly identified with rather different doping levels: the bonding sheet corresponds to a doping level of 0.14, which is slightly underdoped while the antibonding sheet has a doping of 0.27 that is heavily overdoped, giving an overall doping level of 0.20 for the sample. Different superconducting gap sizes on the two Fermi surface sheets are revealed. The superconducting gap on the antibonding Fermi surface sheet follows a standard d-wave form while it deviates from the standard d-wave form for the bonding Fermi surface sheet. The maximum gap difference between the two Fermi surface sheets near the antinodal region is $\sim$2 meV. These observations provide important information for studying the relationship between the Fermi surface topology and superconductivity, and the layer-dependent superconductivity in high temperature cuprate superconductors.

We report high-resolution scanning tunneling microscopy (STM) study of nano-sized Pb islands grown on SrTiO$_{3}$, where three distinct types of gaps with different energy scales are revealed. At low temperature, we find that the superconducting gap (${\it\Delta}_{\rm s}$) in nano-sized Pb islands is significantly enhanced from the one in bulk Pb, while there is no essential change in superconducting transition temperature $T_{\rm c}$, giving rise to a larger BCS ratio 2${\it\Delta}_{\rm s}/k_{_{\rm B}}T_{\rm c} \sim 8.31$ and implying stronger electron-phonon coupling. The stronger coupling can originate from the interface electron-phonon interactions between Pb islands and SrTiO$_{3}$. As the superconducting gap is totally suppressed under applied magnetic field, the Coulomb gap with apparent V-shape emerges. Moreover, the size of Coulomb gap (${\it\Delta}_{\rm C}$) depends on the lateral size of Pb islands ($R$) with ${\it\Delta}_{\rm C}\sim 1/R^{0.35}$, indicating that quantum size effect can significantly influence electronic correlations. Our experimental results shall shed important light on the interplay among superconductivity, quantum size effect and correlations in nano-sized strong-coupling superconductors.

Transition metal dichalcogenides, featuring layered structures, have aroused enormous interest as a platform for novel physical phenomena and a wide range of potential applications. Among them, special interest has been placed upon WTe$_{2}$ and MoTe$_{2}$, which exhibit non-trivial topology both in single layer and bulk as well as pressure induced or enhanced superconductivity. We study another distorted 1T material NbTe$_{2}$ through systematic electrical transport measurements. Intrinsic superconductivity with onset transition temperature ($T_{\rm c}^{\rm onset}$) up to 0.72 K is detected where the upper critical field ($H_{\rm c}$) shows unconventional quasi-linear behavior, indicating spin-orbit coupling induced p-wave paring. Furthermore, a general model is proposed to fit the angle-dependent magnetoresistance, which reveals the Fermi surface anisotropy of NbTe$_{2}$. Finally, non-saturating linear magnetoresistance up to 50 T is observed and attributed to the quantum limit transport.

Frustrated quantum magnets are expected to host many exotic quantum spin states like quantum spin liquid (QSL), and have attracted numerous interest in modern condensed matter physics. The discovery of the triangular lattice spin liquid candidate YbMgGaO$_4$ stimulated an increasing attention on the rare-earth-based frustrated magnets with strong spin-orbit coupling. Here we report the synthesis and characterization of a large family of rare-earth chalcogenides AReCh$_2$ (A = alkali or monovalent ions, Re = rare earth, Ch = O, S, Se). The family compounds share the same structure ($R\bar{3}m$) as YbMgGaO$_4$, and antiferromagnetically coupled rare-earth ions form perfect triangular layers that are well separated along the $c$-axis. Specific heat and magnetic susceptibility measurements on NaYbO$_2$, NaYbS$_2$ and NaYbSe$_2$ single crystals and polycrystals, reveal no structural or magnetic transition down to 50 mK. The family, having the simplest structure and chemical formula among the known QSL candidates, removes the issue on possible exchange disorders in YbMgGaO$_4$. More excitingly, the rich diversity of the family members allows tunable charge gaps, variable exchange coupling, and many other advantages. This makes the family an ideal platform for fundamental research of QSLs and its promising applications.

Orthogonal metal is a new quantum metallic state that conducts electricity but acquires no Fermi surface (FS) or quasiparticles, and hence orthogonal to the established paradigm of Landau's Fermi-liquid (FL). Such a state may hold the key of understanding the perplexing experimental observations of quantum metals that are beyond FL, i.e., dubbed non-Fermi-liquid (nFL), ranging from the Cu- and Fe-based oxides, heavy fermion compounds to the recently discovered twisted graphene heterostructures. However, to fully understand such an exotic state of matter, at least theoretically, one would like to construct a lattice model and to solve it with unbiased quantum many-body machinery. Here we achieve this goal by designing a 2D lattice model comprised of fermionic and bosonic matter fields coupled with dynamic $\mathbb{Z}_2$ gauge fields, and obtain its exact properties with sign-free quantum Monte Carlo simulations. We find that as the bosonic matter fields become disordered, with the help of deconfinement of the $\mathbb{Z}_2$ gauge fields, the system reacts with changing its nature from the conventional normal metal with an FS to an orthogonal metal of nFL without FS and quasiparticles and yet still responds to magnetic probe like an FL. Such a quantum phase transition from a normal metal to an orthogonal metal, with its electronic and magnetic spectral properties revealed, is calling for the establishment of new paradigm of quantum metals and their transition with conventional ones.

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.

The parent compounds of the high-temperature cuprate superconductors are Mott insulators. It has been generally agreed that understanding the physics of the doped Mott insulators is essential to understanding the mechanism of high temperature superconductivity. A natural starting point is to elucidate the basic electronic structure of the parent compound. Here we report comprehensive high resolution angle-resolved photoemission measurements on Ca$_2$CuO$_2$Cl$_2$, a Mott insulator and a prototypical parent compound of the cuprates. Multiple underlying Fermi surface sheets are revealed for the first time. The high energy waterfall-like band dispersions exhibit different behaviors near the nodal and antinodal regions. Two distinct energy scales are identified: a d-wave-like low energy peak dispersion and a nearly isotropic lower Hubbard band gap. These observations provide new information of the electronic structure of the cuprate parent compound, which is important for understanding the anomalous physical properties and superconductivity mechanism of the high temperature cuprate superconductors.

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.

Using the natural orbitals renormalization group (NORG) method, we investigate the screening of the local spin of an Anderson impurity interacting with the helical edge states in a quantum spin Hall insulator. It is found that there is a local spin formed at the impurity site and the local spin is completely screened by electrons in the quantum spin Hall insulator. Meanwhile, the local spin is screened dominantly by a single active natural orbital. We then show that the Kondo screening mechanism becomes transparent and simple in the framework of the natural orbitals formalism. We project the active natural orbital respectively into real space and momentum space to characterize its structure. We confirm the spin-momentum locking property of the edge states based on the occupancy of a Bloch state on the edge to which the impurity couples. Furthermore, we study the dynamical property of the active natural orbital represented by the local density of states, from which we observe the Kondo resonance peak.

The Majorana zero mode (MZM), which manifests as an exotic neutral excitation in superconductors, is the building block of topological quantum computing. It has recently been found in the vortices of several iron-based superconductors as a zero-bias conductance peak in tunneling spectroscopy. In particular, a clean and robust MZM has been observed in the cores of free vortices in (Li$_{0.84}$Fe$_{0.16}$)OHFeSe. Here using scanning tunneling spectroscopy, we demonstrate that Majorana-induced resonant Andreev reflection occurs between the STM tip and this zero-bias bound state, and consequently, the conductance at zero bias is quantized as $2e^{2}/h$. Our results present a hallmark signature of the MZM in the vortex of an intrinsic topological superconductor, together with its intriguing behavior.

The outstanding issue to overcoming atmospheric turbulence on distant imaging is a fundamental interest and technological challenge. We propose a novel scenario and technique to restore the optical image in turbulent environmental by referring to Cyclopean image with binocular vision. With human visual intelligence, image distortion resulting from the turbulence is shown to be substantially suppressed. Numerical simulation results taking into account of the atmospheric turbulence, optical image system, image sensors, display and binocular vision perception are presented to demonstrate the robustness of the image restoration, which is compared with a single channel planar optical imaging and sensing. Experiment involving binocular telescope, image recording and the stereo-image display is conducted and good agreement is obtained between the simulation with perceptive experience. A natural extension of the scenario is to enhance the capability of anti-vibration or anti-shaking for general optical imaging with Cyclopean image.

We perform molecular beam epitaxy growth and scanning tunneling microscopy study of copper diselenide (CuSe₂) films on SrTiO₃(001). Using a Se-rich condition, the single-phase pyrite CuSe₂ grows in the Stranski–Krastanov (layer-plus-island) mode with a preferential orientation of (111). Our careful inspection of both the as-grown and post-annealed CuSe₂ films at various temperatures invariably shows a Cu-terminated surface, which, depending on the annealing temperature, reconstructs into two distinct structures 2×√3 and √3×√3-R30°. The Cu termination is supported by the depressed density of states near the Fermi level, measured by in-situ low temperature scanning tunneling spectroscopy. Our study helps understand the preparation and surface chemistry of transition metal pyrite dichalcogenides thin films.

We review the predictions of quark models for multiquark configurations that are bound or resonant states, and compare different methods for estimating the properties of resonances.

Fractional orbital angular momentum (OAM) vortex beams present a promising way to increase the data throughput in optical communication systems. Nevertheless, high-precision recognition of fractional OAM with different propagation distances remains a significant challenge. We develop a convolutional neural network (CNN) method to realize high-resolution recognition of OAM modalities, leveraging asymmetric Bessel beams imbued with fractional OAM. Experimental results prove that our method achieves a recognition accuracy exceeding 94.3% for OAM modes, with an interval of 0.05, and maintains a high recognition accuracy above 92% across varying propagation distances. The findings of our research will be poised to significantly contribute to the deployment of fractional OAM beams within the domain of optical communications.

We report protonation in several compounds by an ionic-liquid-gating method, under optimized gating conditions. This leads to single superconducting phases for several compounds. Non-volatility of protons allows post-gating magnetization and transport measurements. The superconducting transition temperature $T_{\rm c}$ is enhanced to 43.5 K for FeSe$_{0.93}$S$_{0.07}$, and 41 K for FeSe after protonation. Superconducting transitions with $T_{\rm c} \sim 15$ K for ZrNCl, $\sim$7.2 K for 1$T$-TaS$_2$, and $\sim$3.8 K for Bi$_2$Se$_3$ are induced after protonation. Electric transport in protonated FeSe$_{0.93}$S$_{0.07}$ confirms high-temperature superconductivity. Our $^{1}$H nuclear magnetic resonance (NMR) measurements on protonated FeSe$_{1-x}$S$_{x}$ reveal enhanced spin-lattice relaxation rate $1/^{1}T_1$ with increasing $x$, which is consistent with the LDA calculations that H$^{+}$ is located in the interstitial sites close to the anions.

Devices of electric double-layer transistors (EDLTs) with ionic liquid have been employed as an effective way to dope carriers over a wide range. However, the induced electronic states can hardly survive in the materials after releasing the gate voltage $V_{\rm G}$ at temperatures higher than the melting point of the selected ionic liquid. Here we show that a permanent superconductivity with transition temperature $T_{\rm c}$ of 24 and 15 K is realized in single crystals and polycrystalline samples of HfNCl and ZrNCl upon applying proper $V_{\rm G}$'s at different temperatures. Reversible change between insulating and superconducting states can be obtained by applying positive and negative $V_{\rm G}$ at low temperature such as 220 K, whereas $V_{\rm G}$'s applied at 250 K induce the irreversible superconducting transition. The upper critical field $H_{\rm c2}$ of the superconducting states obtained at different gating temperatures shows similar temperature dependence. We propose a reasonable scenario that partial vacancy of Cl ions could be caused by applying proper $V_{\rm G}$'s at slightly higher processing temperatures, which consequently results in a permanent electron doping in the system. Such a technique shows great potential to systematically tune the bulk electronic state in the similar two-dimensional systems.

Research of infinite-layer nickelates has unveiled a broken translation symmetry, which has sparked significant interest in its root, its relationship to superconductivity, and its comparison to charge order in cuprates. In this study, resonant x-ray scattering measurements were performed on thin films of infinite-layer PrNiO$_{2+\delta}$. The results show significant differences in the superlattice reflection at the Ni $L_{3}$ absorption edge compared to that at the Pr $M_{5}$ resonance in their dependence on energy, temperature, and local symmetry. These differences point to two distinct charge orders, although they share the same in-plane wavevectors. It is suggested that these dissimilarities could be linked to the excess oxygen dopants, given that the resonant reflections were observed in an incompletely reduced PrNiO$_{2+\delta}$ film. Furthermore, azimuthal analysis indicates that the oxygen ligands likely play a crucial role in the charge modulation revealed at the Ni $L_{3}$ resonance.