Tunable bands of electronic image states in nanowire lattices

We demonstrate that suspended arrays of parallel nanowires support bound electron image states with rich band structures. Surprisingly, these Bloch states can be highly detached from the surfaces of the nanowires, similar to the single-tube wave functions. This is because an electron hovering in such a periodic lattice of nanowires is influenced by a Coulombic-like attraction and a centrifugal repulsion, which are both central symmetric around each wire. These novel states could be used in building of waveguides, mirrors, and storage places for Rydberg-like electrons.     

Site-specific phonon density of states discerned using electronic states

We have performed the measurement of the site-specific phonon densities of states (PDOS) discerned using electronic states. As far as we know, no general method could give the site-specific PDOS, although oscillating properties of the individual atoms in nonequivalent positions are not necessarily equivalent. However, the combination of the energy and time domain measurements of the nuclear resonant scattering of synchrotron radiation allows the identification of site-specific PDOS. We measured the site-specific PDOS of iron atoms in magnetite, which is a mixed valent compound, and the difference between partial phonon densities of the iron sites was clearly observed.     

Empty electronic states in solid and liquid nickel

The density of empty electronic states in solid and liquid nickel has been determined employing Auger electron appearance potential spectroscopy. The observed increase of the density-of-states at the Fermi level by a factor of 1.4 in the liquid is in good agreement with available resistivity data. An increase of d-holes from 0.6 to 1.0 upon fusion is also found and interpreted in terms of a reduced d-d-interaction in the liquid state.     

Spin-polarized electronic density of states in amorphous iron

The spin-polarized electronicd-band density of states in amorphous iron are reported using recursion method. The magnetic moment of amorphous iron is found to be almost as high as BCC iron. This lends support to the view expressed by Kemény et al. that the extrapolation of experimental results obtained on samples containing less than 2% impurities to deduce the magnetic moment of pure amorphous iron may not be justified.     

The density of unoccupied electronic states in copper

The density of unoccupied electronic states in Cu has been measured employing soft X-ray appearance-potential spectroscopy (SXAPS). The L_III le     

On spectral density of electronic states in disordered systems

In the present paper, the averaged spectral density of electronic states, 〈?(k, E)〉, has been computed for three-dimensional disordered systems with spherical well type atomic potentials. The formula for 〈?(k, E)〉 is derived by using a realistic perturbational approach that takes propagator modification into account, together with a handy approximation due toBallentine. 〈?(k, E)〉 has been computed for various sets of potential strength and concentration, and the dependence of 〈?(k, E)〉 upon these parameters has been discussed. The motivation behind the computations reported here, is to examine the circumstances under which the electron motion in disordered systems is expected to be almost free electronic. Our principal finding is that a simultaneous existence of weak electron-scatterer interaction-potential and high density of scatterers would tend to make the motion of an electron in a disordered system almost like that of a free one.     

Dependence of Tc on electronic density of states

From the Eliashberg gap equations generalized to include approximately an energy dependence in the electron density of states N(ε) we compute the functional derivative of the critical temperature T_c with N(ε). It is found to be a rapidly decreasing function of the increasing energy away from the Fermi energy. In an appropriate limit, a comparison with the predictions of the McMillan equation shows that it is inadequate in a study of δT_c/δN(ε).     

Pseudogap in the electronic density of states of superconducting glasses

Two loop order results for the electronic density of states (DOS) of both Ising- and XY-type superconducting glass phases are presented. Maximal depression of the DOS by critical fluctuation corrections to its finite mean field value is found to occur at the Fermi energyE _F . The theory is renormalizable and exponentiation of the loop expansion yields (E _F)=0 for the DOS in two dimensions and for arbitrarily small disorder. It is also concluded that the DOS assumes nonzero values, when either |E–E _F|, or magnetic field H, or temperature T become nonzero. A pseudogap (atT=0,H=0) or a smeared gap (forH0 orT0) is thus obtained with a DOS-minimum at the Fermi level. A rough estimate of the effective width is given. In three dimensions, the DOS atE _F vanishes like (n _c ^I –n)^1/2 for the Ising-type glass and like (n _c ^XY –n)¹ for the XY-type glass as the impurity concentrationn exceeds characteristic values. At second loop order, the calculation contains a nontrivial indication of a lower critical dimension two.     

The role of electronic density of states in metallic Lanthanum

Observations of X-ray photoabsorption in metallic Lanthanum in the vicinity of the 3d _5/2-edge are given. Two separated absorption peaks are detected at the quantum energies =830.6eV and =834.0eV. The results are interpreted according to the model given in communication I–IV [1].     

Engineering bands of extended electronic states in a class of topologically disordered and quasiperiodic lattices

We show that a discrete tight-binding model representing either a random or a quasiperiodic array of bonds can have the entire energy spectrum or a substantial part of it absolutely continuous, populated by extended eigenfunctions only, when atomic sites are coupled to the lattice locally, or non-locally from one side. The event can be fine-tuned by controlling only the host–adatom coupling in one case, while in two other cases cited here an additional external magnetic field is necessary. The delocalization of electronic states for the group of systems presented here is sensitive to a subtle correlation between the numerical values of the Hamiltonian parameters – a fact that is not common in the conventional cases of Anderson localization. Our results are analytically exact, and supported by numerical evaluation of the density of states and electronic transmission coefficient.     

Distribution of electron density of states in allowed bands and interband absorption in amorphous semiconductors

Different types of electronic transitions and the corresponding spectral characteristics of the absorption coefficient of amorphous semiconductors, where the energy of absorbed photons exceeds the mobility band gap, have been investigated. Partial spectral characteristics of the absorption coefficient and, correspondingly, the distributions of the electron density of the states involved in these optical transitions are obtained for the case where the electron densities of states in the allowed bands and the tails of these bands change with energy according to the power and exponential laws, respectively. The conditions for the occurrence of a peak in the spectral characteristic of the interband absorption coefficient are determined.     

Exotic electronic states in the world of flat bands:From theory to material

It has long been noticed that special lattices contain single-electron flat bands(FB) without any dispersion. Since the kinetic energy of electrons is quenched in the FB, this highly degenerate energy level becomes an ideal platform to achieve strongly correlated electronic states, such as magnetism, superconductivity, and Wigner crystal. Recently, the FB has attracted increasing interest because of the possibility to go beyond the conventional symmetry-breaking phases towards topologically ordered phases, such as lattice versions of fractional quantum Hall states. This article reviews different aspects of FBs in a nutshell. Starting from the standard band theory, we aim to bridge the frontier of FBs with the textbook solidstate physics. Then, based on concrete examples, we show the common origin of FBs in terms of destructive interference,and discuss various many-body phases associated with such a singular band structure. In the end, we demonstrate real FBs in quantum frustrated materials and organometallic frameworks.     

Global energy spectra of bands and density of states in a class of two-tile systems

Electronic properties of a general class of one-dimensional two-tile systems are calculated exactly. The systems containing periodic crystals, generalized Fibonacci quasicrystals, generalized Thue-Morse aperiodic lattices and even other two-tile aperiodic lattices, can be divided into two different families which are constructed by the inflation rules: {A, B}{A ^m11 B ^m12,A ^m21 B ^m22} and {A, B}{A ⁿ¹¹ B ⁿ¹²,B ⁿ²¹ A ⁿ²²}, respectively. As typical examples, global spectra of bands and density of states in some two-tile aperiodic systems are numerically calculated. Some interesting properties are obtained.     

Quasi-particle spectrum and density of electronic states in AA- and AB-stacked bilayer graphene

The present work deals with the analysis of the quasi-particle spectrum and the density of states of monolayer and bilayer (AB- and AA-stacked) graphene. The tight binding Hamiltonian containing nearest-neighbor and next-nearest neighbor hopping and onsite Coulomb interaction within two triangular sub-lattice approach for monolayer graphene, along-with the interlayer coupling parameter for bilayer graphene has been employed. The expressions of quasi-particle energies and the density of states (DOS) are obtained within mean-field Green’s function equations of motion approach. It is found that next-nearest-neighbour intralayer hopping introduce asymmetry in the electronic states above and below the zero point energy in monolayer and bilayer (AA- and AB-stacked) graphene. The behavior of electronic states in monolayer and bilayer graphene is different and highly influenced by interlayer coupling and Coulomb interaction. It has been pointed out that the interlayer coupling splits the quasi-particle peak in density of states while the Coulomb interaction suppresses the bilayer splitting and generates a gap at Fermi level in both AA- and AB-stacked bilayer graphene. The theoretically obtained quasi-particle energies and density of states in monolayer and bilayer (AA- and AB-stacked) graphene has been viewed in terms of recent ARPES and STM data on these systems.     

Densities of states in the unoccupied bands of palladium in the region of ΓL

Features in the angle-resolved secondary electron emission from a Pd(111) surface are compared with regions of high one-dimensional densities of states in calculated band structures. Earlier measurements at normal exit are confirmed and extended over a range of angles away from ΓL and a new feature which disperses rapidly with angle is detected; very good agreement with an RAPW band structure is found.     

On the electronic density of states of the transition metals

A superposition model is suggested to describe the electronic density of states curves of binary alloys with the aid of those of the component metals. It is based on a charge transfer between the different atomic cells. The application of this model to different spectroscopic methods studying the density of states brings up the question of the localizing and averaging properties of the corresponding experiments.     

On the electronic density of states of the transition metals

XIS measurements of the elements Ir, Pt and Au are reported. High precision and reproducibility is obtained by the application of a “π/2-method” which approximates a Bragg angle of 90° at the dispersing crystal. Theoretical densities of states exist for Pt and Au. The agreement with the measured isochromats is good. A rigid-band model for Ir, Pt, and Au is ruled out by the measurements. Rather they suggest (combined with results of photoemission experiments) a narrowing of thed-bands from Ir through Pt to Au. Moreover, thed-band of Ir lies relative to thesp-band at a lower energy than thed-bands of Pt and Au. A fitting parameter concerning the experimental resolution is explained and considered as a possible indication of localization for XIS.