共查询到20条相似文献,搜索用时 31 毫秒
1.
Hopping conduction in the Landau level tails in GaAs-AlxGa1-xAs heterostructures at low temperatures
G. Ebert K. von Klitzing C. Probst E. Schuberth K. Ploog G. Weimann 《Solid State Communications》1983,45(7):625-628
We have investigated the temperature dependence of the transverse conductivity σxx in the two-dimensional Shubnikov—de Haas oscillation minima in GaAs-AlxGa1-xAs heterostructures at temperatures between 10mK and 1 K. We found that for σxx ? σxx (max), where σxx (max) is the conductivity in the corresponding oscillation maxima, the results agree qualitatively with a theory recently published by Ono, predicting , but are not consistent with the estimated T0-values. 相似文献
2.
The threshold behaviour of pion production presented in our earlier work is successfully compared with the new SPEAR data. By using duality and sum rules we derive FT(π+)(x) ≈ FL(π+)(x) ≈ FT(π0)(x) ? FL(π0)(x) for x near 1. An accompanying results is for large s. 相似文献
3.
Victor Elias 《Physics letters. [Part B]》1977,68(4):335-338
The Callan-Gross relation is shown to be consistent with MIT-SLAC data for for x ? 0.33 in deep inelastic eN scattering, despite the fact that these data are taken in the large Q2 region where F1 and F2 individually exhibit scaling violation. Comparison is made with asymptotic freedom predictions, and color excitation is proposed to explain large values of at small x. 相似文献
4.
We study the correlation function 〈σ0x(t)σnx(0)〉 of the transverse Ising model in a critical field whose hamiltonian is . At an arbitrary temperature T we relate the autocorrelation to a Fredholm determinant. Moreover at T = 0 the correlations are given by a Painlevé V function for all n. The long-time asymptotic behavior of this function is found and the connection problem is studied. This result contains oscillatory terms which are related to the density of states at the Brillouin zone boundary. 相似文献
5.
The time dependence of microwave absorption was measured for the J = 2-1 and J = 3-2 transitions of OCS under on- and off-resonant conditions utilizing Stark and source modulation, respectively. The two effective pressure parameters obtained under the two conditions, which correspond to and , respectively, according to the Bloch equation, are different beyond experimental error; the difference is 0.94 ± 0.38 (2.5σ) MHz/Torr for J = 2?1. This difference was also determined to be 1.19 ± 0.30 MHz/Torr from the dependence of the nutation frequency on the microwave power. 相似文献
6.
For the model at T = 0 four susceptibilities have been calculated exactly on a sequence of finite square lattices and extrapolated to the infinite square lattice. For the ferromagnet χzz = 0 while χxx ~ N2.9; for the antiferromagnet and . 相似文献
7.
It is shown explicitly for a soluble model that a random spin system can have an entropy which is non-analytic at (H = 0, T = 0), with and/or non-vanishing in the T → 0 limit, while nevertheless Nernst's law is satisfied. 相似文献
8.
In this note we determine the oscillator strengths for the dipole absorption of neutral bound excitons in direct gap semiconductors, using our previously obtained 35-term Page and Fraser type wave function, and taking into account the detailed electronic structure as well as the electron-hole exchange interaction.The envelope part of the oscillator strengths varies considerably with the electron-hole mass ratio , and is maximum for the (D0, X)- complex when σ = 0.4. For typical σ-values (σ? 0.1–0.2), . But when σ approaches zero, the overlapping of the electron and the hole envelope wave functions of the (A0,X)-complex decreases progressively so that the oscillator strength also decreases and tends to zero.In the case of zinc-blende materials (Td) and positive spin-orbit coupling at , we confirm that the line strength for transitions to or from or level of the (A0, X)-complex is equal to one quarter of the line strength to or from the level.In the case of CdS, where our computed values are only in qualitative agreement with the experimental values, we discuss the use of the phenomenological result of Rashba. 相似文献
9.
Yu. Oročko 《Reports on Mathematical Physics》1979,15(2):163-172
Let ,m? 1.Consider the operatorT0 = ?Δ+q with domain consisting of all bounded measurable functions , having bounded support, for which the distribution ?Δu+qu belongs to . The main result of the paper is essential self-adjointness of . The proof is independent of a method due to Kato who recently established the self-adjointness of a maximal Schrödinger operator corresponding to such potential. 相似文献
10.
The one-electron momentum distribution function for an electron gas is investigated by a diagrammatic analysis of perturbation theory. It is shown that has the following exact asymptotic form for large k (k ? pF; pF, the Fermi momentum): , where g?(0) is the zero-distance value of the spin-up-spin-down pair correlation function. The physical implications of the above asymptotic form are discussed. 相似文献
11.
M.C. Leung 《Solid State Communications》1974,15(5):879-882
We investigate the properties of a quasi-unidimensional system which exhibits Peierls instability at Tc(μ), where μ is the Fermi energy as measured from the middle of the conduction band. Tc(μ) decreases as 6μ6 increases. The phonon-drag diagrams contribute to fluctuation conductivity, which is proportional to , if |μ| > 1.056 Tc(0). The Kohn Anomalies do not occur at 2kF unless μ = 0 or |μ| ? T. 相似文献
12.
Robert W. Field Richard A. Gottscho E. Miescher 《Journal of Molecular Spectroscopy》1975,58(3):394-413
No perturbation between two valence states of NO has ever been identified, although many valence-Rydberg and several Rydberg-Rydberg perturbations have been extensively studied. The first valence-valence crossing to be experimentally documented for NO is reported here and occurs between the 15N18O B2Π (v = 18) and B′2Δ (v = 1) levels. No level shifts larger than the detection limit of 0.1 cm?1 are observed at the crossings near and ; two crossings involving higher rotational levels could not be examined. Semi-empirical calculations of spin-orbit and Coriolis perturbation matrix elements indicate that although the electronic part of the interaction is large, a small vibrational factor renders the 15N18O B (v = 18) ? B′ (v = 1) perturbation unobservable. Semi-empirical estimates are given for all perturbation matrix elements of the operators and which connect states belonging to the configurations , , and . 相似文献
13.
We derive and compare with experimental data the bound , where α is the fine-structure constant, mp the proton mass, ν0 the photo-pion production threshold, σtot and are the unpolarized total hadronic photo-absorption cross section on protons and the unpolarized forward differential cross section for proton Compton scattering at photon-lab energy ν′, and λ and ν1 are any real numbers. We derive similar bounds on proton and neutron magnetic moments. 相似文献
14.
Anil K. Bhatnagar B. Bhanu Prasad N. Ravi R. Jagannathan T.R. Anantharaman 《Solid State Communications》1982,44(6):905-909
Amorphous Fe40Ni40B20 (VITROVAC 0040) alloy has been investigated using 57Fe Mössbauer Spectroscopy. The Curie temperature Tc is found to be well defined and is 695 ± 1 K. The quadrupole splitting just above Tc is 0.64 mm sec?1. The crystallization temperature is 698 ± 2 K, close to but definitely above Tc. The average hyperfine field Heff(T) of the glassy state shows a temperature dependence of indicative of the existence of spin wave excitations. The values of and are found to be 0.40 and 0.06, respectively, for T/Tc ? 0.72. At temperatures close to Tc, Heff(T) varies as (1 ? T/Tc)β where β is one of the critical exponents and its value is found to be 0.29 ± 0.02. 相似文献
15.
T. P. McPharlin D. O. Caldwell J. P. Cumalat A. M. Eisner D. L. Fancher R. J. Morrison F. V. Murphy T. R. Risser S. J. Yellin 《Physics letters. [Part B]》1980,90(4):479-484
Using 20.5 GeV electrons on protons, we measured inclusive π0's (of transverse momentum, pT, from 0 to 1.4 GeV/c) produced by virtual photons of energy, ν, from 4 to 16.5 GeV and four-momentum squared, q2, from ?1.8 to ?8.5 (GeV/c)2. Comparing with charged pion data, we find , supporting the quark model. Photon knockout of a quark is favored as the interpretation of these data because of scaling in z = Eπ/ν and similarity in z-dependence of other pion production data. Consistent with this interpretation are the dependence of 〈pT〉 on q2, the azimuthal dependence, and fits to the constituent interchange model. We also observe a possible pT?4 dependence at large |q2| over a limited pT range. 相似文献
16.
A. Berglund T. Buran P.J. Carlson C.J.S. Damerell I. Endo A.R. Gillman V. Gracco R.J. Homer M.J. Hotchkiss A. Lundby M. Macri B.N. Ratcliff A. Santroni T. Tso F. Wickens J.A. Wilson 《Physics letters. [Part B]》1975,57(1):100-104
For the first time, the reactions π+p→K+∑+ and K?p→π?∑+ have been studied in the same apparatus. This has been done at an adequately high momentum (10.1 GeV/c) to allow a check of the prediction of exchange degeneracy, that the differential cross sections should be converging at high energy. We have measured the cross section for momentum transfers t between tmin and t = ?0.3 (GeV/c)2. We find that for both reactions the differential cross section shows an exponential fall, with no deviations right in to t =tmin (where some other experiments have shown a dip in the cross section). Furthermore, we find the magnitude of the differential cross sections to be closely similar at t = 0, with a ratio However, the slope for the positive reaction is about 19% steeper than that for the negative reaction. 相似文献
17.
P.L. Lijnse P.J.Th. Zeegers C.Th.J. Alkemade 《Journal of Quantitative Spectroscopy & Radiative Transfer》1973,13(10):1033-1045
Weighted average quenching cross sections for the Rb(52P) doublet by N2 and H2O were determined in flames with temperatures ranging from 1500 to 2500 K by measuring the fluorescence efficiency. The values found are and over the entire temperature range. At a temperature of 1720 K, mixing cross sections were obtained for the same doublet with N2, H2, O2 and H2O molecules. The cross sections found are: , ; , , , . The ratios σ12/σ21 were measured independently and were found to agree with the detailed- balance condition within 3 per cent. A critical comparison of the flame values with previous literature data on N2-cross sections shows that both mixing and quenching cross sections are temperature dependent in the range from 300 to 2500 K. 相似文献
18.
Yu.M. Antipov V.A. Bessubov N.P. Budanov Yu.P. Gorin S.P. Denisov S.V. Klimenko A.A. Lebedev Yu.V. Mikhailov A.I. Petrukhin S.A. Polovnikov V.N. Roinishvili D.A. Stoyanova F.A. Yotch 《Physics letters. [Part B]》1978,76(2):235-236
The differential cross sections and of inclusive J/ψ production by 43 GeV/c π? off Be, Cu and W nuclei have been measured. Fitting we observed the increase of α with pt2. 相似文献
19.
Using the similarity of the effective potentials seen by ions in metals a reduced phonon equation of state is derived. It is shown that the melting point Tm(0) and the atomic volume Ω0 at T = 0 K and at p = 0 are suitable macroscopic parameters for scaling ? and σ characterizing the interatomic potentials of metals having similar structures. The temperature and pressure dependence of thermodynamical quantities reduced with the above parameters are discussed and the results are compared with the experiment. It is shown that the pressure dependence of the reduced thermodynamic quantities can be described by the pressure dependence of the scaling parameters Tm(p) and Ω0(p).The general form of the reduced equation of state (containing the electronic contributions as well) obtained gives that the reduced pressure is a universal function of the following reduced variables: the volume, temperature, de Broglie wavelength, Gibbs free energy of electrons (Efo is the Fermi energy at T = 0 K) and depe of the valence z as well. It is shown that is a function of and is approximately constant within the same sub-group of the periodic table. 相似文献
20.
The emission and excitation spectra of the aromatic thioketone xanthione have been measured in Shpolskii matrices at 15 K. Under these conditions a sharp and rich vibrational structure is observed in the lowest triplet and the first and second excited singlet states. The phosphorescence excitation spectrum places the origin of the T1 ← S0 transition at 15 143 cm?1, while that of the absorption is tentatively assigned to the band at 16 093 cm?1. The phosphorescence spectrum, which shows only a weak CS stretch vibrational band, is dominated by ring vibrations. In accordance with the previous analysis of ODMR measurements, it is suggested that T1 and T2 states are energetically very close, thereby resulting in a lowest triplet state of heavily mixed n, , character. No mirror-image relationship is found between the relatively strong S2 → S0 fluorescence and the excitation spectrum of the transition. The latter is dominated by a long, pronounced 336-cm?1 progression. 相似文献