Dispersive Analysis of Excited Glueball States

Motivated by the determination for the spin-parity quantum numbers of the X(2370)meson at BESⅢ,we extend our dispersive analysis on hadronic ground states to excited states.The idea is to start with the dispersion relation which a correlation function obeys,and subtract the known ground-state contribution from the involved spectral density.

Density of excess modes below the first phonon mode in four-dimensional glasses

Glasses are known to possess low-frequency excess modes beyond the Debye prediction.For decades,it has been assumed that evolution of low-frequency density of excess modes D(ω) with frequency ω follows a power-law scaling:D(ω)~ω~γ.However,it remains debated on the value of γ at low frequencies below the first phonon-like mode in finitesize glasses.Early simulation studies reported γ=4 at low frequencies in two-(2D),three-(3D),and four-dimensional(4D)glasses,whereas recent observations in 2D and 3D glasses suggested γ=3.5 in a lower-frequency regime.It is uncertain whether the low-frequency scaling of D(ω)~ω^(3.5) could be generalized to 4D glasses.Here,we conduct numerical simulation studies of excess modes at frequencies below the first phonon-like mode in 4D model glasses.It is found that the system size dependence of D(ω) below the first phonon-like mode varies with spatial dimensions:D(ω) increases in2D glasses but decreases in 3D and 4D glasses as the system size increases.Furthermore,we demonstrate that the ω^(3.5)scaling,rather than the ω~4 scaling,works in the lowest-frequency regime accessed in 4D glasses,regardless of interaction potentials and system sizes examined.Therefore,our findings in 4D glasses,combined with previous results in 2D and 3D glasses,suggest a common low-frequency scaling of D(ω)~ ω^3.5) below the first phonon-like mode across different spatial dimensions,which would inspire further theoretical studies.

Analyzing the surface passivity effect of germanium oxynitride:a comprehensive approach through first principles simulation and interface state density

High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy resolution.The surface passivation of HPGe has become crucial for achieving an extremely low energy threshold.In this study,first-principles simulations,passivation film preparation,and metal oxide semiconductor(MOS)capacitor characterization were combined to study surface passivation.Theoretical calculations of the energy band structure of the -H,-OH,and -NH_(2) passivation groups on the surface of Ge were performed,and the interface state density and potential with five different passivation groups with N/O atomic ratios were accurately analyzed to obtain a stable surface state.Based on the theoretical calculation results,the surface passivation layers of the Ge_(2)ON_(2) film were prepared via magnetron sputtering in accordance with the optimum atomic ratio structure.The microstructure,C-V,and I-V electrical properties of the layers,and the passivation effect of the Al/Ge_(2)ON_(2)/Ge MOS were characterized to test the interface state density.The mean interface state density obtained by the Terman method was 8.4×10^(11) cm^(-2) eV^(-1).The processing of germanium oxynitrogen passivation films is expected to be used in direct dark matter detection of the HPGe detector surface passivation technology to reduce the detector leakage currents.

Local density of optical states calculated by the mode spectrum in stratified media

The local density of optical states(LDOS)is an important physical concept,which can characterize the spontaneous emission of microcavities.In order to calculate the LDOS,the relationship between the mode spectrum and the LDOS is established.Then,based on the transfer matrix method and the effective resonator model,the leaky loss of the leaky mode and the mode spectrum in the one-dimensional photonic bandgap crystal waveguide are calculated,results of which indicate that the mode spectrum can characterize the leaky loss of the leaky mode.At last,the density of optical states(DOS),and the LDOS in each layer are calculated.The partial DOS and the partial LDOS in the quantum well,related to the fundamental leaky mode,can be used to find out the optimal location of the quantum well in the defect layer to couple more useful photons into the lasing mode for lasers.

Discrete vortex bound states with a van Hove singularity in the vicinity of the Fermi level

A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS lies exactly at the Fermi level and also at the middle of the band, a zero-energy state and other higher-energy states whose energy ratios follow integer numbers emerge. These discrete vortex bound state peaks undergo a splitting behavior when the VHS or Fermi level moves away from the middle of the band. Such splitting behavior will eventually lead to a new arrangement of quantized vortex core states whose energy ratios follow half-odd-integer numbers.

Engineering d-band states of(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material for photocatalytic syngas production

The d-band states of catalytic materials participate in adsorbing reactive intermediate species and determine the catalytic behaviors in CO_(2)reduction reactions.However,surface d-band states relating to the photocatalytic CO_(2)reduction reactions behaviors are rarely concerned.Herein,a slightly amount of Cd^(2+)is decorated on the surface of(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material(Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4))to tune the surface d-band states for improved CO_(2)+2reduction reactions.The Cd/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)is fabricated via the facile ions-exchange method to make that slightly Zn2+is substituted by Cd^(2+).The Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)exhibits much enhanced photocatalytic activity in CO_(2)reduction reactions to produce CO and water splitting to produce H_(2).Physical characterizations show that the energy band structure is not changed obviously.Density functional theory reveals that Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)possesses a closer shift of d-band center to Fermi level than(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4),suggesting easier adsorption of CO_(2)reduction reactive intermediates after Cd^(2+)decoration.Further calculations confirm that a relatively reduced adsorption Gibbs energy of reactive intermediates in CO_(2)reduction reaction is required on Zn atoms in Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material,benefiting the photocatalytic CO_(2)reduction reactions.This work engineers surface d-band states by surface Cd^(2+)decoration,which gives an effective strategy to design highly efficient photocatalysts for syngas production.

The Gap Labelling Integrated Density of States for a Quasi Crystal Universe Is Identical to the Observed 4.5 Percent Ordinary Energy Density of the Cosmos

Condense matter methods and mathematical models used in solving problems in solid state physics are transformed to high energy quantum cosmology in order to estimate the magnitude of the missing dark energy of the universe. Looking at the problem from this novel viewpoint was rewarded by a rather unexpected result, namely that the gap labelling method of integrated density of states for three dimensional icosahedral quasicrystals is identical to the previously measured and theoretically concluded ordinary energy density of the universe, namely a mere 4.5 percent of Einstein’s energy density, i.e. E(O) = mc2/22 where E is the energy, m is the mass and c is the speed of light. Consequently we conclude that the missing dark energy density must be E(D) = 1 - E(O) = mc2(21/22) in agreement with all known cosmological measurements and observations. This result could also be interpreted as a strong evidence for the self similarity of the geometry of spacetime, which is an expression of its basic fractal nature.

Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current us bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.

Revealing the potential of apparent critical current density of Li/garnet interface with capacity perturbation strategy

Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.

Wigner Function：from Ensemble Average of Density Operator to Its Matrix Element in Entangled Pure States

We show that the Wigner function (an ensemble average of the density operator ρ, Δ is the Wigner operator) can be expressed as a matrix element of ρ in the entangled pure states. In doing so, converting from quantum master equations to time-evolution equation of the Wigner functions seems direct and concise. The entangled states are defined in the enlarged Fock space with a fictitious freedom.

Enhancement of refresh time in quasi-nonvolatile memory by the density of states engineering

The recently reported quasi-nonvolatile memory based on semi-floating gate architecture has attracted extensive attention thanks to its potential to bridge the large gap between volatile and nonvolatile memory.However,the further extension of the refresh time in quasi-nonvolatile memory is limited by the charge leakage through the p-n junction.Here,based on the density of states engineered van der Waals heterostructures,the leakage of electrons from the floating gate to the channel is greatly suppressed.As a result,the refresh time is effectively extended to more than 100 s,which is the longest among all previously reported quasi-nonvolatile memories.This work provides a new idea to enhance the refresh time of quasi-nonvolatile memory by the density of states engineering and demonstrates great application potential for high-speed and low-power memory technology.

Low-frequency hybridized excess vibrations of two-dimensional glasses

One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow D_(exc)(ω)~ω^(2)in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.

Spontaneous-emission control by local density of states of photonic crystal cavity

The local density of states （LDOS） of two-dimensional square lattice photonic crystal （PhC） defect cavity is studied. The results show that the LDOS in the centre is greatly reduced, while the LDOS at the point off the centre （for example, at the point （0.3a, 0.4a）, where a is the lattice constant） is extremely enhanced. Further, the disordered radii are introduced to imitate the real devices fabricated in our experiment, and then we study the LDOS of PhC cavity with configurations of different disordered radii. The results show that in the disordered cavity, the LDOS in the centre is still greatly reduced, while the LDOS at the point （0.3a, 0.4a） is still extremely enhanced. It shows that the LDOS analysis is useful. When a laser is designed on the basis of the square lattice PhC rod cavity, in order to enhance the spontaneous emission, the active materials should not be inserted in the centre of the cavity, but located at positions off the centre. So LDOS method gives a guide to design the positions of the active materials （quantum dots） in the lasers.

Valence band structure and density of states effective mass model of biaxial tensile strained silicon based on k·p theory

After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k·p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states （DOS） effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal-oxide semiconductor field effect transistor （MOSFET）. It also a provides valuable reference for biaxial tensile strained silicon MOSFET design.

Spin-Split Joint Density of States in GdN

We present an investigation of the optical constants of the near stoichiometric GdN films. Transmission and reflection spectra are collected for the paramagnetic and the ferromagnetic GdN in the photon energy range of 0.5-5.5 eV. In the ferromagnetic phase, behaviors of minority and majority spin states are specifically focussed on, which indicate spin-split joint density of states. The results confirm the LSDA＋U estimates of energy gap associated with the majority-spins and also the magnitude of spin splitting.

Wigner Function:from Ensemble Average of Density Operator to Its One Matrix Element in Entangled Pure States

We show that the Wigner function W = Tr(△ρ) (an ensemble average of the density operator ρ, △ is theWigner operator) can be expressed as a matrix element of ρ in the entangled pure states. In doing so, converting fromquantum master equations to time-evolution equation of the Wigner functions seems direct and concise. The entangledstates are defined in the enlarged Fock space with a fictitious freedom.

Local density of states of dc-biased superlattices with time-dependent imperfection

The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. The calculation of the local density of states shows that new states will emerge between the resonant Wannier-Stark states as a result of the intervention of time-dependent impurity potential, and the increase in electric field strength of impurity will result in the growing of the number of new states between the gaps of neighbouring Stark ladders.

Methods for Derivation of Density Matrix of Arbitrary Multi-Mode Gaussian States from Its Phase Space Representation

We present a method for derivation of the density matrix of an arbitrary multi-mode continuous variable Gaussian entangled state from its phase space representation.An explicit computer algorithm is given to reconstruct the density matrix from Gaussian covariance matrix and quadrature average values.As an example,we apply our method to the derivation of three-mode symmetric continuous variable entangled state.Our method can be used to analyze the entanglement and correlation in continuous variable quantum network with multi-mode quantum entanglement states.

Density of States in Two-Dimensional Square Lattices Around Half Filling with Strong Impurities

We calculate the lowest-order quantum-interference correction to the density of states (DOS) of weakly-disordered two-dimensional (2D) tight-binding square lattices around half filling. The impurities are assumed to be randomly distributed on small fractions of the sites, and have a-strong potential yielding a unitary-limit scattering. In addition to the usual diffusive modes in the retarded-advanced channel, there appear diffusive pi modes in the retarded-retarded (or advanced-advanced) channel due to the existence of particle-hole symmetry. It is found that the pi-mode diffuson gives rise to a logarithmic suppression to the DOS near the band center, which prevails over the positive correction contributed by pi-mode cooperon. As a result, the DOS is subject to a negative total correction. This result is qualitatively different from the divergent behavior of the DOS at the band center predicted previously for disordered 2D two-sublattice models with the particle-hole symmetry.

Study of Electronic Density of States: Zintl Alloys

In the present work the electronic density of states of liquid,viz.,Zintli alloys,have been studied only at the composition of their maximum resistivity to have an elementary idea about the behaviors of the alloys with respect to nearly free electron behavior.The study reveals that the anomalous electronic behavior of liquid Li-Pb,Na-Pb,Li-Sn,and Na-Sn can be attributed to the preferential ordering of unlike atoms.