共查询到20条相似文献,搜索用时 62 毫秒
1.
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
2.
L. Gunther 《Physics letters. A》1973,45(5):367-368
We introduce a Landau type theory of the Peierls instability-superconductor transition involving two complex order parameters. Under a particular inequality condition among expansion parameters, the theory predicts that the superfluid conductivity should vary as above the critical region and as below the critical region. 相似文献
3.
《Journal of Physics and Chemistry of Solids》2004,65(8-9):1381-1390
4.
We present approximate analytic calculation of the functional derivative , where Tc is the superconducting critical temperature and is the electron-phonon spectral function, within the “square-well model” for the phonon mediated electron-electron interaction and weak coupling limit is the Debye energy). It is found that where λ is the familiar electron-phonon coupling parameter and is a universal function of the reduced frequency . We compare this formula with accurate numerical results for several weak coupling superconductors. The overall agreement is good 相似文献
5.
The softening of an acoustic and an optical phonons in Hg2Br2 has been investigated by means of the light scattering technique.It has been observed that the cube of the frequency of the soft optical phonon varies proportionally with the temperature below Tc.An expression for the relation of the elastic constant C66 to the temperature has been derived from the phenomenological thermodynamic potential function. The observed temperature dependence of the elastic constant and the optical phonon frequency is described when we assume that the order parameter Q varies as . 相似文献
6.
It is shown that the thermal fluctuations depin the charge density wave of the Peierls Fröhlich state pinned by impurities at absolute zero temperature. The critical temperature, Td, of this depinning is estimated as where m1 and γ0 are the mass of the collective mode and the pinning frequency at T = 0. 相似文献
7.
R.P. Goddard 《Nuclear Physics A》1977,291(1):13-20
Deuteron-nucleus optical model calculations which include two types of tensor spin-orbit interactions are compared. The interactions considered are of the forms where the operators Tr and Tp are defined as . Here, are the deuteron spin, position, and momentum operators, respectively. If a physically reasonable radial dependence VTP(r) is used, the S-matrix elements (and hence all observables) calculated using a Tp tensor potential are found to be similar to those calculated using a suitably chosen Tr potential, provided that the incident deuteron energy is small compared to the real central potential. At higher deuteron energies, the differences between the effects of Tr and Tp potentials are more pronounced. 相似文献
8.
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
9.
The self-energies of acoustic phonons in ion implanted and laser annealed ultraheavily doped n-type Si have been measured by Brillouin scattering. The corresponding softening of the elastic constants has been estimated from the observed phonon softening and compared it with theory. At high doping levels () the effect of the increase in atomic mass on the phonon frequency is observed in the case of doping with As. From the increase in the linewidths of the Brillouin lines with doping, the optical absorption coefficients for as a function of doping are determined. 相似文献
10.
The absorption and MCD spectra of the , , and spin-allowed transitions of Cr3+ in K2NaGaF6 are reported. It is shown that transitions to the . states are induced by T1u vibratio the other spin-allowed transition, , there are three competing intensity mechanisms: electric dipole induced by T1u vibrations, electric dipole induced by T2u vibrations and magnetic dipole, and an estimate is made of the relative importance of these. The magnetic dipole zero-phonon line is observed to be accompanied by a vibrational sideband for which the coupling is predominantly with T2u vibrations. Other weak transitions are observed in MCD spectra and their origin briefly discussed. 相似文献
11.
It is shown that the low-temperature conductivity in two-dimensional impurity band of n-type inversion layer under strong magnetic field is . Therefore the effective conductivity of inversion layer at Shubnikov-de Haas conductivity minima may be very high at low temperature. 相似文献
12.
Measurements of the temperature and pressure dependences of the resistivity of the pseudo-one-dimensional ternary compound Tl2Mo6Se6 are presented. We find that the conductivity parallel to the highly conducting c-axis is enhanced by pressure and the superconducting transition temperature Tc is suppressed by pressure at a rate kbar?1. These results are discussed in relation to the current models of transport in one-dimensional conductors. 相似文献
13.
Acoustic phonon damping in Nb due to superconductivity is accurately measured by the inelastic neutron scattering technique. The phonon line widths can be characterized by the reduced parameters and T/Tc, and are in good qualitative agreement with the calculation by Bobetic based on the BCS theory. 相似文献
14.
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
15.
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
16.
Heinz Pagels 《Physics letters. [Part B]》1979,87(3):222-226
We discuss several features of dynamical symmetry breaking in gauge theories of strong, weak and electromagnetic interactions. We speculate that in some such theories the fine structure constant calculable. A possible solution of the strong P and T violation problem in QCD by dynamical symmetry breaking is indicated. Self-energy divergences are absent in such models and we compute the finite electromagnetic self-energy of a quark in QCD. The mass hierarchy problem is examined. We find models in which the fermion-gauge boson mass ratio is (), where g is a gauge boson coupling, which could account for the origin of weak interactions. 相似文献
17.
A simple theoretical derivation is given to show that one may expect a hard core for the phonon frequency at the transition temperature. This approach implies that the frequency of the phonon will follow instead of that predicted by soft mode theory. Our expression should be valid whenever a Brownian sublattice exists in the crystal. 相似文献
18.
The reactions 17O(d, t) 16O and 17O(d, τ)16N have been investigated at Ed = 52 MeV. Energy spectra of tritons and τ-particles have been measured simultaneously up to excitation energies of 22 MeV in 16O and 10 MeV in 16N, respectively. Spectroscopic factors have been obtained by a DWBA analysis of the measured angular distributions. From the comparison of the t- and τ-spectra analog (T = 1) states in 16O could be identified and the distribution of T = 0 and T = 1 spectroscopic strengths could be deduced. Nearly the total and hole strengths have been found and the particle-hole multiplets could be located both for T = 0 and T = 1. The average residual interactions in both shell-model configurations turned out to be strikingly different. 相似文献
19.
We consider semi-inclusive reactions of the type p + p → (particle with large pT) + n charged particles + neutrals, and propose the following scaling law for the distribution function of the large-pT particle produced in association with n charged particles. This scaling rule is shown to be consistent with present information on single-particle spectra and average associated multiplicities at large pT. Also, we show that if the associated multiplicity were to continue to increase linearly with pT, then moments of the multiplicity distribution would increase like powers of s. 相似文献
20.
B.P. Antonyuk 《Solid State Communications》1978,25(12):971-975
A possibility of the central peak appearance in crystals with low concentration of small-radius polarons is pointed out. The intensity of the central peak increases sharply with the softening of the phonon mode in the vicinity of the structural phase transition . The peak width γ0 is determined by the probability W of the polaron hopping between the sites γ0 = K02a2W. 相似文献