Thermopower of a semiconductor film with parabolic potential in a strong magnetic field

Relationships for the transverse magnetothermopower of a semiconductor film with parabolic potential are derived for the cases of nondegenerate statistics and strong degeneracy. It is demonstrated that, in the case of strong degeneracy, quantum levels lying below the Fermi level intersect the Fermi level with an increase in the magnetic field, which leads to jumpwise oscillations of the thermopower magnitude.     

Mesoscopic magnetic states in metallic alloys with strong electronic correlations: a percolative scenario for CeNi 1-x Cux

We present evidence for the existence of magnetic clusters of approximately 20 A in the strongly correlated alloy system CeNi 1-x Cux (0.7相似文献   

Thermopower of Al1−x Six solid solutions in vicinity of lattice instability

The thermopower coefficient as a function of temperature, S(T), has been measured in nonequilibrium superconductors, such as Al_1−x Six substitutional solid solutions and Al-Si alloys on various decay stages. When aluminum is substituted with silicon, the contribution to the thermopower due to phonon-drag effects, which are dominant in pure aluminum at low temperatures, is suppressed, and low-temperature anomalies in S(T) detected in compositions near lattice instability limit are determined by the diffusion component of the thermopower. The low-temperature anomalies in the thermopower and the notable increase in the coefficient in front of the linear term in S(T) are attributed to effects of thermopower renormalization due to the electron-phonon interaction enhancement with “soft modes” in the face-centered cubic (FCC) lattice of Al_1−x Six solid solutions. The nature of these anomalies in S(T) is analyzed in terms of the Kaiser and Reizer-Sergeev models. Zh. éksp. Teor. Fiz. 113, 339–351 (January 1998)     

Direct observation of the modulation of the 4f-electron orbital state by strong p-f mixing in CeSb

Low-temperature x-ray diffraction experiment has been carried out to investigate the 4 f-electron state of the low carrier density system CeSb which shows complicated magnetic phase diagrams at low temperatures. The scattering pattern of the satellite peaks observed in the magnetically ordered state AFP3 is explained well by the model which takes into account both the lattice and charge modulations corresponding to the complex magnetic structure. The present result gives direct evidence for the strong modulation of the 4 f-electron orbital state in CeSb due to the combined effect of the strong p-f mixing and carrier localization.     

Electronic structure of LaIrIn5and f-electron character in its related Ce-115 compounds

LaIrIn_5 is a reference compound of the heavy-fermion superconductor LaIrIn_5. The lack of f electrons in LaIrIn_5 indicates that there should not be any f electron participating in the construction of its Fermi surface. Thus the electronic structure comparison between LaIrIn_5 and LaIrIn_5 provides a good platform to study the properties of f electrons. Here angle-resolved photoemission spectroscopy(ARPES) measurements and density functional theory(DFT) calculations are performed to study the electronic structures of LaIrIn_5 and LaIrIn_5. We find the valence band structures of the two materials are similar to each other, except for the absence of f bands in LaIrIn_5. By analyzing the Fermi crossings of the three conduction bands of the two materials quantitatively,we find the volumes of the electron pockets α and β around the M′point become larger from LaIrIn_5 to LaIrIn_5, while the hole pocket γ around the Γ′point becomes smaller. Together with the calculation results, we confirm that this is mainly originated from the f-electron contribution, while the lattice-constant difference between LaIrIn_5 and LaIrIn_5 only has a finite influence. We also give a summary of the f-electron character in its related Ce-115 heavy fermion compounds. Our results may be essential for the complete microscopic understanding of the 115 compounds and the related heavy-fermion systems.     

Modulational instability of matter waves under strong nonlinearity management

We study modulational instability of matter-waves in Bose-Einstein condensates (BEC) under strong temporal nonlinearity-management. Both BEC in an optical lattice and homogeneous BEC are considered in the framework of the Gross-Pitaevskii equation, averaged over rapid time modulations. For a BEC in an optical lattice, it is shown that the loop formed on a dispersion curve undergoes transformation due to the nonlinearity-management. A critical strength for the nonlinearity-management strength is obtained that changes the character of instability of an attractive condensate. MI is shown to occur below (above) the threshold for the positive (negative) effective mass. The enhancement of number of atoms in the nonlinearity-managed gap soliton is revealed.     

4f-electron localization in CexLa 1-xM In5 with M=Co, Rh, or Ir

de Haas-van Alphen measurements on Ce(x)La(1-x)MIn(5) yield contrasting types of behavior that depend on whether M=Co and Ir or M=Rh. A stronger x-dependent scattering in the case of M=Co and Ir is suggestive of a stronger relative coupling, J/W, of the conduction electrons to the 4f electrons, which would then account for the development of a heavy composite Fermi-liquid state as x-->1. The failure of a composite Fermi-liquid state to form for any x in the case of M= Rh is shown to be inconsistent with theoretical models that propose antiferromagnetism to result from spin-density-wave formation.     

CDW instability of electron gas in a strong magnetic field

It is shown that within the Hartree-Fock approximation the electron gas in the quantum limit of a strong magnetic field has an instability as the temperature is lowered toward the charge density wave state with an wave-vector which has finite components in the directions not only parallel but also perpendicular to the field. The critical temperature, T_c, is estimated under the assumption of T_c??_F?ω_c, where ?_F and ω_c are the Fermi energy of the non-interacting system and the cyclotron frequency respectively.     

Thermopower for a molecule with vibrational degrees of freedom

We study a simple model to describe resonant tunneling through an organic molecule between two conducting leads, taking into account the vibrational modes of the molecule. We solve the model approximately analytically in the weak coupling limit and give explicit expressions for the thermopower and Seebeck coefficient. The behavior of these two quantities is studied as function of model parameters and temperature. For a certain regime of parameters a rather peculiar variation of the thermopower and Seebeck coefficient is observed.     

强湍流效应下激光大气传输短曝光光斑统计分析

利用数值模拟的方法,对强湍流效应下激光大气传输焦平面短曝光光斑的统计特性进行了初步分析,并与实验结果进行了对比。结果表明：在强湍流效应下,焦平面短曝光光斑破碎成一系列的小光斑,这些破碎光斑的等效半径与爱里斑半径近似相等;接收器中心置于光轴轴心处,当接收孔径等于爱里斑直径时,接收的均值光强最大。     

强湍流效应下激光大气传输短曝光光斑统计分析

利用数值模拟的方法,对强湍流效应下激光大气传输焦平面短曝光光斑的统计特性进行了初步分析,并与实验结果进行了对比。结果表明:在强湍流效应下,焦平面短曝光光斑破碎成一系列的小光斑,这些破碎光斑的等效半径与爱里斑半径近似相等;接收器中心置于光轴轴心处,当接收孔径等于爱里斑直径时,接收的均值光强最大。     

Electromagnetic radiation and instability of superthermal particles in a magnetoactive plasma with strong small-scale irregularities

The electromagnetic radiation of superthermal electrons in a magnetoactive plasma with strong small-scale irregularities is calculated. The emissive power of such a medium is found. The flux density of electromagnetic radiation I_f is determined for an optically thin medium. The values of I_f are estimated for different ionospheric conditions. The induced radiation of a directed electron beam of charged particles in a magnetoactive plasma with such irregularities is studied. The gain (absorption) factor is derived. The possibility of electromagnetic instability in different ionospheric conditions is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 3, pp. 286–300, March, 1996.     

Band conduction effects in the ESR spectra of semiconducting Na0.01V2O5

We report on the temperature- and orientation dependence of the ESR linewidth of d-electrons in semiconducting Na_0.01V₂O₅. The observed line narrowing results from hopping of the d-electrons between localized states. At higher temperatures a line broadening occurs which is due to excitation of the d-electrons into a conduction band. The corresponding activation energies, determined from ESR measurements, agree with values derived from electronic conductivity.     

Fluctuation instability of the Dirac Sea in quark models of strong interactions

A number of exactly integrable (quark) models of quantum field theory that feature an infinite correlation length are considered. An instability of the standard vacuum quark ensemble, a Dirac sea (in spacetimes of dimension higher than three), is highlighted. It is due to a strong ground-state degeneracy, which, in turn, stems from a special character of the energy distribution. In the case where the momentumcutoff parameter tends to infinity, this distribution becomes infinitely narrow and leads to large (unlimited) fluctuations. A comparison of the results for various vacuum ensembles, including a Dirac sea, a neutral ensemble, a color superconductor, and a Bardeen–Cooper–Schrieffer (BCS) state, was performed. In the presence of color quark interaction, a BCS state is unambiguously chosen as the ground state of the quark ensemble.     

Photoemission investigation of hexagonal BN: Band structure and atomic effects

Photoemission valence band spectra and the polarization dependent photoyield at the B K-edge are compared to calculated densities of states. Excitonic effects at the edge are discussed. For the decay of exciton and ionized core the influence of atomic effects is shown.     

Off-peak saturation effects of beam-plasma instability

For beam-plasma instability in the absence of a magnetic field, hybrid simulations produce almost identical results to those of particle simulations (both agree with linear and nonlinear analyses), but with much reduced computing cost and noise level. With the verification by simulations, it is shown that the saturation level is very strongly influenced by the discrete wave number spectrum, sometimes giving different, by an order of magnitude, results by choosing slightly different off-peak (in growth rate curve) parameters, which must be considered in most simulations (whether hybrid or particle or whether magnetized or unmagnetized)