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1.
Using the self-consistent pseudopotential method, we have calculated the binding energy of the image states for the (0001)
, and
surfaces of beryllium. It is shown for the (0001) face that there exists a pronounced resonance image state with n=1 and energy −0.95 eV at the point
of the surface Brillouin zone. In the
surface, which has a wide band gap in the vicinity of the vacuum level, the calculated image state with n=1 at the point
has energy −1.2 eV and is a surface state of gap type. For the
face in the vicinity of the point
band gaps are absent. However, the symmetry of the bulk states near the vacuum level enables the existence of a resonance
image state with n=1 and energy −0.6 eV.
Fiz. Tverd. Tela (St. Petersburg) 41, 935–940 (June 1999) 相似文献
2.
Xing-jiang ZHOU 《Frontiers of Physics》2009,4(4):427
In this paper, we present a brief review on our angle-resolved photoemission measurements on the band structure, Fermi surface, and superconducting gap of the newly-discovered FeAs-based high temperature superconductors. (1) The Fermi surface of the FeAs-based compounds are characterized by the hole-like Fermi surface sheets near Γ (0, 0) and the existence of singular Fermi spots near M(π, 相似文献
3.
I. A. Devyatov M. Yu. Kupriyanov 《Journal of Experimental and Theoretical Physics》1998,87(2):375-381
Elastic resonant tunneling through a single localized state in an insulating layer (I-layer) situated in the constriction
zone between two thick superconducting electrodes is investigated theoretically, and the current-voltage characteristic (IVC)
of the structure is calculated. The accompanying analysis leads to the prediction that an appreciable current can flow through
the structure, not at |eV|=2Δ (Δ is the modulus of the order parameter of the superconducting electrodes) as in the case of an ordinary SIS junction,
but at |eV|⩾Δ, and also that the IVC can acquire segments of negative differential resistance in the case of tunneling through a single
localized state. Averaging of the IVC over an ensemble of localized states distributed uniformly throughout the volume of
the I-layer and with respect to the energy near the chemical potential min the limit Γ0/Δ≫1 (Γ0 is the half-width of the resonance line of the localized state) produces a smaller excess current than in a junction of the
SNS type. It is shown that the IVC’s exhibit a transition from an excess current to a deficit current as Γ0 decreases in the high-voltage range.
Zh. éksp. Teor. Fiz. 114, 687–699 (August 1998) 相似文献
4.
The effect of smooth interface potential on the electron tunneling in the GaAs/AlAs(111) structures with thin layers is studied using the pseudopotential method. The transition region between the structure components
is represented by a half-period of the hexagonal (GaAs)
3(AlAs)3
(111) superlattice. It is shown that the allowance for the smooth potential results in a decrease in the Γ-L-mixing, Fano-resonance
narrowing, and disappearance of interface states at the GaAs/AlAs(111) interface as compared to the abrupt-interface model. The shifts of the lowest Γ-and L-resonances observed for the structures
with the layer thickness <2 nm amount to ∼0.1 eV, which is in good agreement with the behavior of levels in quantum wells.
The transmission coefficient of electrons with the energies 0–0.5 eV above the GaAs conduction-band bottom obtained by multivalley calculation is close to that calculated with allowance for the lowest conduction
band states Γ
1
(1)
and Γ
1
(2)
of superlattice and Γ
1 and L
1 of binary crystals. This indicates that a two-valley superlattice model of the smooth GaAs/AlAs(111) interface can be developed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 7–13, July, 2007. 相似文献
5.
L. Šamaj 《Journal of statistical physics》2007,128(6):1415-1428
In the equilibrium statistical mechanics of classical Coulomb fluids, the long-range tail of the Coulomb potential gives rise
to the Stillinger–Lovett sum rules for the charge correlation functions. For the jellium model of mobile particles of charge
q immersed in a neutralizing background, the Stillinger–Lovett sum rules give the charge and second moment of the screening
cloud around a particle of the jellium. In this paper, we generalize these sum rules to the screening cloud induced around
a pointlike guest charge Zq immersed in the bulk interior of the 2D jellium with the coupling constant Γ=β
q
2 (β is the inverse temperature), in the whole region of the thermodynamic stability of the guest charge amplitude Z>−2/Γ. The derivation is based on a mapping technique of the 2D jellium at the coupling Γ = (even positive integer) onto a
discrete 1D anticommuting-field theory; we assume that the final results remain valid for all real values of Γ corresponding
to the fluid regime. The generalized sum rules reproduce for arbitrary coupling Γ the standard Z=1 and the trivial Z=0 results. They are also checked in the Debye–Hückel limit Γ→0 and at the free-fermion point Γ=2. The generalized second-moment
sum rule provides some exact information about possible sign oscillations of the induced charge density in space. 相似文献
6.
M. Debbichi A. Ben Fredj A. Bhouri N. Bouarissa M. Said 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):17-23
Taking into account the recent advances in the epitaxial growth of
single-crystal InN leading to a drastic re-evaluation of its fundamental
energy band gap, we have studied the electronic properties of
InNxP1-x (x < 0.01) ternary alloy. Using the empirical
pseudopotential method under the virtual crystal approximation, combined
with the Harrison bond orbital model, the band gap at Γ, X and L
points, the effective masses of the Γ valley and the electronic
charge densities are calculated as a function of nitrogen composition. The
fitted expressions of the energy band gaps indicate that the bowing
parameter at Γ reached a broad value for very low nitrogen
incorporation (
).
Furthermore, the band gap at Γ point decreases drastically with
increasing nitrogen composition up to 1%. The elastic constants and the
optical phonon frequencies are also reported. Our theoretical results
provide a good agreement with the available data. 相似文献
7.
P. Jiricek M. Cukr I. Bartos M. Adell T. Strasser W. Schattke 《Czechoslovak Journal of Physics》2006,56(1):21-26
The electron structure of GaAs(100)-c(4 × 4) has been studied by means of angular-resolved photoelectron spectroscopy for photon energies (20–40) eV. The sample
was prepared by molecular beam epitaxy in-situ at the BL41 beamline of the MAX I storage ring of the Max-lab in Lund.
Photon energy variation helped in separating dispersing bulk features from nondispersing surface features in the energy distribution
curves recorded at normal emission. Two sets of peaks were related to bulk transitions from the two topmost E(k
⊥) branches of the valence band of GaAs and one more set came from the surface state in the center of the 2D Brillouin zone.
Good agreement was found between experimental bulk dispersion branches and theoretical calculations based on realistic final
state dispersion. The surface state peak, hardly visible at 20 and 22 eV photon excitations, gets clearly enhanced at higher
excitation energies.
In contrast to earlier measurements of this kind, two major differences have been found: (i) clearly developed surface state
peak just below the top of the v alence band, (ii) absence of a large peak in the electron energy distribution at around −6.5eV
below the valence band top.
Presented at the X-th Symposium on Suface Physics, Prague, Czech Republic, July 11–15, 2005. 相似文献
8.
We performed comparative quasi-synchronous measurements of radiowave attenuation by snowfalls on a close-to ground radio ray
path of 1025 m long at frequencies 138 and 247 GHz. We showed that during some periods of a snowfall there is a stable, almost
functional correlation between the attenuation coefficients at frequencies 138 GHz (Γ(138)) and 247 GHz (Γ(247)). In two of
six recorded events such a correlation persisted during the entire snowfall. There were some occasions when the relationship
between Γ(138) and Γ(247) had a “hysteresis” form. Analysis of all the data as a whole showed a linear correlation between
Γ(138) and Γ(247) with a correlation coefficient of about 0.97. The average value of the ratio Γ(247)/Γ(138), which characterizes
the frequency dependence of wave damping in snowfalls, was found to be equal to 3.8, its measured values being in the range
between 1.6 and 6.2. Results of the experiment are compared with data from other measurements.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 42, No. 2, pp. 103–108, February 1999. 相似文献
9.
We report the development of a method for recording the low-temperature (T=6 K) near-IR inelastic light scattering spectra and the observation of electronic scattering on the transitions 1s
3/2(Γ8) → 2s
3/2(Γ8) between the ground and excited states of different shallow acceptor centers in a n-type semi-insulating crystal si-GaAs (n=1.0 × 108 cm−3) and in a doped p-InP crystal (p=3.6×1017 cm−3). Moreover, a new line, associated with the transition 1s
3/2(Γ 8) → 2p
3/2(Γ8) and due to a dielectric local mode, recorded for the first time in the spectra of narrow-gap semiconductors, was found in
the residual-frequency band in the p-InP spectrum between TO(Γ) and LO (Γ) phonons.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 334–339 (10 March 1998) 相似文献
10.
B. Indrajit Sharma Jameson Maibam R. S. Paul R. K. Thapa R. K. Brojen Singh 《Indian Journal of Physics》2010,84(6):671-674
Energy band structure of NbC and NbN are calculated using generalized gradient approximation (GGA) within density functional
theory (DFT) including five high symmetry points W, L, Γ, X and K. The lowest band corresponds to 2s band of non metal (C and N) atoms and the next lowest band is formed by 2p nonmetal. The decomposing points of t
2g
states (Γ
25), e
g
states (Γ
12) and C or N 2p states (Γ
15) show interesting behavior different from earlier reports. 相似文献
11.
S. A. Mikhnov 《Journal of Applied Spectroscopy》1999,66(6):994-998
It has been found that the F-band of optical absorption which is observed in ψ-irradiated NaF crystals consists of three overlapping
bands. The band at 345 nm of width 40 nm is independent of the impurity composition of the crystals; it disappears upon exposure
to radiation at 345 nm and appears again upon annealing at 460±15 K for 15 min. This band is correlatable in intensity with
the superfine structure of an EPR spectrum. The width (65–110 nm) and the spectral position (355–375 nm) of the second band
depend on the impurity composition of the crystal. The band of width 90–110 nm at 320–325 nm disappears upon annealing and
appears after exposure to light simultaneously with the disappearance of an EPR signal. It is established that the band at
345 nm is caused by quasimolecules based on fluorine atoms, that at 355–375 nm is triggered by F-centers with a different
impurity composition near the haloid vacancy, and the band at 320–325 nm owes its appearance to F-centers in a negatively
charged state (F′).
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 849–853, November–December, 1999. 相似文献
12.
I. Ya. Gerlovin Yu. K. Dolgikh Yu. P. Efimov I. V. Ignat’ev I. A. Nedokus 《Physics of the Solid State》1998,40(5):756-757
We have experimentally investigated the low-temperature (10 K) luminescence and reflection spectra of a gradient GaAs/AlAs
superlattice. We have examined the behavior of phonon satellites in the vicinity of the X-Γ resonance. Smooth passage through the resonance was achieved by scanning an exciting light beam along the surface of a
gradient sample. Based on our experimental results, we have determined the functional dependence of the Γ-X mixing potential on the resonance detuning.
Fiz. Tverd. Tela (St. Petersburg) 40, 822–823 (May 1998) 相似文献
13.
J. Sjakste V. Tyuterev N. Vast 《Applied Physics A: Materials Science & Processing》2007,86(3):301-307
Interactions between excited electrons and short-wavelength (intervalley) phonons in GaAs are studied using density functional
theory for the conduction bands, and density functional perturbation theory for phonon frequencies and matrix elements of
the electron–phonon interaction. We have calculated the deformation potentials (DPs) and the average intervalley scattering
time 〈τ〉. The integration of the scattering probabilities over all possible final states in the Brillouin zone has been performed
without any ad hoc assumption about the behavior of the electron–phonon matrix elements nor the topology of the conduction
band. For transitions from the L point to Γ valley (within the first conduction band), we find 〈τ〉L to be 1.5 ps at 300 K, in good agreement with time-resolved photoluminescence experiment. We discuss the difference between
our calculated DPs, and effective parameters used in Monte Carlo simulations of optical and transport properties of semiconductors.
The latter are based on Conwell’s model, in which electron–phonon interaction is described by one single constant and a parabolic
model is used for conduction bands. We deduce the effective DP from our 〈τ〉, and compare it to our calculated DPs. We conclude
that only effective DPs obtained from a full calculation of 〈τ〉 are relevant parameters for Monte Carlo simulations.
PACS 71.10-w; 72.10.Di; 71.55.Eq 相似文献
14.
In the framework of a simple spin-boson Hamiltonian we study an interplay between dynamic and spectral roots to stochastic-like
behavior. The Hamiltonian describes an initial vibrational state coupled to discrete dense spectrum reservoir. The reservoir
states are formed by three sequences with rationally independent periodicities 1; 1 ± δ typical for vibrational states in
many nanosize systems (e.g., large molecules containing CH2 fragment chains, or carbon nanotubes). We show that quantum evolution of the system is determined by a dimensionless parameter
δΓ, where Γ is characteristic number of the reservoir states relevant for the initial vibrational level dynamics. When δΓ
> 1 spectral chaos destroys recurrence cycles and the system state evolution is stochastic-like. In the opposite limit δΓ
< 1 dynamics is regular up to the critical recurrence cycle k
c
and for larger k > k
c
dynamic mixing leads to quasi-stochastic time evolution. Our semi-quantitative analytic results are confirmed by numerical
solution of the equation of motion. We anticipate that both kinds of stochastic-like behavior (namely, due to spectral mixing
and recurrence cycle dynamic mixing) can be observed by femtosecond spectroscopy methods in nanosystems in the spectral window
1011–1013 s−1 相似文献
15.
The dependence of the intrinsic line width Γ of electron and hole states due to inelastic scattering on the wave vector k
∥ in the occupied surface state and the first image potential state on the Cu(111) and Ag(111) surfaces has been calculated
using the GW approximation, which simulates the self-energy of the quasiparticles by the product of the Greens’s function
and the dynamically screened Coulomb potential. Different contributions to the relaxation of electron and hole excitations
have been analyzed. It has been demonstrated that, for both surfaces, the main channel of relaxation of holes in the occupied
surface states is intraband scattering and that, for electrons in the image potential states, the interband transitions play
a decisive role. A sharp decrease in the intrinsic line width of the hole state with an increase in k
∥ is caused by a decrease in the number of final states, whereas an increase in Γ of the image potential state is predominantly
determined by an increase of its overlap with bulk states. 相似文献
16.
B. Aengenvoort W. Korten H. Hübel S. Chmel A. Görgen U.J. van Severen W. Pohler R. Zinken T. Härtlein C. Ender F. Köck P. Reiter D. Schwalm F. Schindler J. Gerl R. Schubart F. Azaiez S. Bouneau J. Duprat I. Deloncle 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):359-364
Three mini-orange conversion–electron spectrometers and four Euroball Ge Cluster detectors have been used for γ–e- coincidence spectroscopy of superdeformed 135Nd. Transitions within the superdeformed band are shown to have the expected E2 multipolarity. The 766.5–keV transition which
links the band to a positive-parity state has a conversion coefficient consistent with M1 multipolarity. Consequently, positive
parity is deduced for the superdeformed band. No evidence for E0 transitions was found.
Received: 22 December 1997 / Revised version: 19 January 1998 相似文献
17.
G. Albertini G. Bossi B. Dubini M. G. Ponzi Bossi F. Rustichelli 《Il Nuovo Cimento D》1988,10(11):1385-1398
Summary The interaction of cholesterol with membranes is particularly interesting as the cholesterol concentration influences membrane
stability and permeability by inducing changes in the structure and dynamics of the constituent lipid molecules. On the other
hand, cholesterol is present in the atherosclerotic plaques and in some skin diseases, like xanthomas and xantelasmas. An
investigation was performed on the Γ phase in a cholesterol-distearoyl phosphatidyl choline (DSPC) mixture by using X-ray
diffraction and differential scanning calorimetry. The cholesterol/DSPC molar ratio was 35/65 and DSPC-to-water weight ratio
was 1/3. The Γ phase appears at sufficiently high concentration of cholesterol and it is characterized by interchain positional
order considerably lower than in theL
β′ andP
β′ phases but higher than in theL
∝ liquid crystalline phase of pure lecithin in excess water. The results suggest that a lateral phase separation exists in
the temperature range of existence of the Γ phase. The other phase Γ′ appears to be richer in cholesterol. The (Γ+Γ′) toL
∝ phase transition was investigated and the temperature dependence of the in-plane correlation length in the Γ phase was determined.
A very weak enthalpy peak was observed at the chain melting transition, confirming the highly disordered nature of phases
Γ and Γ′.
Work presented at the First USSR-Italy Bilateral Meeting on Liquid Crystals held in Portonovo, Ancona (Italy), September 30–October
2, 1987. 相似文献
18.
We calculate the warping of the bulk dispersion of InSb in thek-space using different models for the bulk band structure near the Γ point. It is shown that the dispersion of the conduction
band Γ6 is well described by the simplified six-band model, while the fourteen-band model is more accurate for the valence bands. 相似文献
19.
M. Weinelt M. Kutschera R. Schmidt C. Orth T. Fauster M. Rohlfing 《Applied Physics A: Materials Science & Processing》2005,80(5):995-1003
The electronic structure and electron dynamics at a Si(100) surface is studied by two-photon photoemission (2PPE). At 90 K the occupied Dup dangling-bond state is located 150±50 meV below the valence-band maximum (VBM) at the center of the surface Brillouin zone ̄ and exhibits an effective hole mass of (0.5±0.15)me. The unoccupied Ddown band has a local minimum at ̄ at 650±50 meV above the VBM and shows strong dispersion along the dimer rows of the c(4×2) reconstructed surface. At 300 K the Ddown position shifts comparable to the Si conduction-band minimum by 40 meV to lower energies but the dispersion of the dangling-bond states is independent of temperature. The surface band bending for p-doped silicon is less than 30 meV, while acceptor-type defects cause significant and preparation-dependent band bending on n-doped samples. 2PPE spectra of Si(100) are dominated by interband transitions between the occupied and unoccupied surface states and emission out of transiently and permanently charged surface defects. Including electron–hole interaction in many-body calculations of the quasi-particle band structure leads us to assign a dangling-bond split-off state to a quasi-one-dimensional surface exciton with a binding energy of 130 meV. Electrons resonantly excited to the unoccupied Ddown dangling-bond band with an excess energy of about 350 meV need 1.5±0.2 ps to scatter via phonon emission to the band bottom at ̄ and relax within 5 ps with an excited hole in the occupied surface band to form an exciton living for nanoseconds. PACS 73.20.At; 79.60.Bm; 79.60.Dp; 79.60.Ht 相似文献
20.
Intervalley electron scattering by phonons in (AlAs)1(GaAs)3(001) superlattices is studied using the pseudopotential method and a phenomenological model of the bonding forces. The deformation
potentials between the conduction band extrema of the superlattice involving short-and long-wavelength phonons are calculated.
It is shown that the mixing of states from the zinc-blende L valleys plays a greater role in intervalley scattering in a superlattice than the Γ-X mixing. In particular, due to L-L mixing, the Γ-X
3 transitions, analogous to Γ-L transitions in zinc blende, have higher intensities than the analogues of Γ-X transitions (Γ1-M
5 and (Γ1-Γ3 transitions). The deformation potentials averaged over the scattering channels in the superlattice agree with the corresponding
potentials in a solid solution, but all transitions in the superlattice have higher intensities for the lower states. 相似文献