Magnetic field dependent dielectric function for zero-gap semiconductors

Using the random phase approximation and the Yafet wave functions the inter and intraband static dielectric functions of degenerate zero-gap semiconductors placed in a magnetic field are calculated in the long wavelength limit. It is shown that the values of the dielectric function for gapless semiconductors differ considerably from the result obtained previously for the one-band model with parabolic energy dispersion ands-type wave functions. Finally the dielectric function is used to find the static screening of a point impurity charge.     

Possibility of negative resistance effect in zero-gap semiconductors

It is believed that for α-Sn-like zero-gap semiconductor under uniaxial tensile stress, negative differential resistance effect may be obtained. If this effect is indeed found, new possibilities for building solid state oscillators will be opened up.     

Energy gap induced by magnetic field in zero-gap semiconductors

The k_z dependence of magnetic sub-bands in α-Sn and HgTe is studied theoretically using the method of Luttinger in the spherical approximation. It is demonsrated that the external magnetic field opens a gap of forbidden energy in these zero-gap semiconductors. Possible experimental consequences of this effect are examined.     

Anisotropic effects induced by magnetic field in zero-gap semiconductors

The magnetic sub-band structure in zero-gap semiconductors α—Sn and HgTe is calculated and shown to depend strongly on the field orientation. This effect is discussed in connection with high-field transport and optical phenomena. It is demonstrated that a transverse electric field acts to increase the magnetically induced gap in α—Sn and to decrease it in HgTe.     

Calculation of the dielectric function for highly excited polar semiconductors

The optical dielectric function of an electron-hole plasma in highly excited polar semiconductors with a direct band gap is calculated by solving a Bethe-Salpeter equation for the polarization function. The screening of the Coulomb potential is treated in a damped phonon-plasmon-pole approximation. We include the complex dynamical self-energy corrections as well as electron-hole correlations.Project of the Sonderforschungsbereich Frankfurt/Darmstadt, financed by special funds of the Deutsche Forschungsgemeinschaft     

Local-field corrections to the static dielectric function of semiconductors: A model study

We present results for the macroscopic static dielectric function at small wave vector q for semiconductors, including the local-field corrections (LFCs). We have used the Penn model for our study. Our calculations demonstrate that LFCs depend on the parameters characterizing a semiconductor. Our calculations are in agreement with the calculations based on more detailed band structures.     

Field and frequency-dependent dielectric constant of quasi-one-dimensional semiconductors

The “conducting box” polarization model proposed by the present author and Belyantsev [4] which explains successfully the value and the frequency dependence of the giant dielectric constant of the one-dimensional organic semiconductor Me φ₃ As(TCNQ)₂, predicts that the dielectric constant drops in the high-electric-field region. The typical electric field strength is of the order of 20 V cm^?1.     

A note on the theory of dielectric dispersion in inhomogeneous dielectrics and semiconductors

A three-layer equivalent circuit for an inhomogeneous dielectric or semiconductor is described. This circuit can be used for describing dielectric dispersion in ferrites and other materials. Barrier layers, localized at inhomogeneities, are shown to be responsible for the low-frequency dispersion in ferrites.     

Anomalous magnetoresistance in a zero-gap semiconductor

As a result of the anomalous screening in symmetry induced zero-gap semiconductor, such as gray tin, the classical magnetoresistance of a p-type sample at low temperature is expected to have an anomalous dependence on the magnetic field in the sense that it may deviate significantly from the usual H² behavior.     

Thermal dielectric function

Thermal dielectric functions ε(k, ω) for homogeneous electron gas were determined and discussed. The ground state of the gas is described by the Fermi-Dirac momentum distribution. The low and high temperature limits of ε(k,ω) were related to the Lind-hard dielectric function and to ε(k,ω) derived for Boltzmann and for classical momentum distributions, respectively.     

On the positron work function for a metal with a dielectric coating

It is shown that a dielectric coating on the metal surface may change the sign of the positron work function. Calculations are performed using the Kohn-Sham method for polycrystals and faces of Al, Cu, and Zn.     

Adhesion of metals and semiconductors analyzed by a dielectric formalism

This paper discusses a model of the adhesive interaction of metals and semiconductors, based on a dielectric formalism and using the concepts of collective excitations — plasmons of the electron-ion system. Expressions are obtained in terms of the jellium model in the longwavelength approximation for the adhesion energy and the adhesive interaction force and are determined via the dispersion dependences of the energies of surface plasma oscillations for various materials whose surfaces are separated by a gap of arbitrary magnitude. The adhesion energies and the adhesive interaction forces are calculated for a number of simple and transition metals and semiconductors, and the adhesion characteristics are also obtained for the contact of the given materials with an insulating medium. Fiz. Tverd. Tela (St. Petersburg) 39, 964–967 (June 1997)     

On the dielectric response function and dispersion relation in strongly coupled magnetized dusty plasmas

Using the generalized viscoelastic fluid model, we derive the dielectric response function in a strongly coupled dusty magnetoplasma which reveals two different dust acoustic(DA) wave modes in the hydrodynamic and kinetic limits. The effects of the strong interaction of dust grains and the external magnetic on these DA modes, as well as on the shear wave are examined. It is found that both the real and imaginary parts of DA waves are significantly modified in strongly coupled dusty magnetoplasmas. The implications of our results to space and laboratory dusty plasmas are briefly discussed.     

On the theory of electroabsorption in amorphous semiconductors

The coefficient of electroabsorption between localized states of an amorphous semiconductor in the weak electric field is evaluated. The decrease in the relative EA ₂/ ₂ F ₂ with increasing energy deficitE _g- is found to be caused by the linear decrease in the density of thermally unstable localized states in the external electric field with the absolute value of the energy inside the gap. If we take into account exciton effects in the EA the qualitative picture does not change, only the slope and the position of the turnover of the relative change in the EA depends on the exciton binding energy.Dedicated to Professor Miroslav Trlifaj on the occasion of his sixtieth birthday.The authors are indebted to T. F. Mazets (A. I. Ioffe PTI, Leningrad) for directing our attention to these problems and for useful discussions during the stay of one of us (E. M.) in the A. F. Ioffe Physico-Technical Institute. We thank also Ing. . Barta for useful discusions.