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.     

On the resonance two phonon absorption in zero-gap semiconductors

The resonance two phonon process is used to explain innormal value and temperature dependence of oscillator strength of additional phonon mode observed in zero-gap semiconductors.     

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.     

Inversion asymmetry spin level splitting in zero-gap semimagnetic semiconductors

We present a new model to interpret recent measurements on Hg_1-xMn_xSe which show an angular dependence of the nodes in the Shubnikov-de Haas amplitude. The model is based on an infinite Hamiltonian matrix including inversion asymmetry terms. We additionally took into account the exchange interaction, typical for Semimagnetic Semiconductors. By truncating the matrix we can calculate the electron energy levels, allowing us to describe the experimentally observed nodal field positions.     

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     

The dielectric function of holes in semiconductors of zinc-blende structure

A closed analytic expression for the q and ω dependent dielectric function of the degenerate gas of holes in a zinc-blende or diamond structure semi-conductor is obtained in the random phase approximation (RPA). The limits of q → 0 and ω → 0 are examined and a comparison with previous developments is given. Significant deviations from the earlier results are found.     

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.     

A quantum mechanical expression for the lattice contribution to the total dielectric function of semiconductors

Effects of electron-electron and electron-phonon optical interactions on the lattice dielectric function of the doped polar semiconductors are investigated. A new expression for the lattice contribution to the dielectric function is derived using the remarkable Zubarev double-time Green function. A numerical calculation for the case of GaN is done to highlight the accuracy of the model. The results obtained are in agreement with the available experimental data and reproduce the main features observed in Raman scattering spectra.     

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.     

On the nonlinear dielectric function of CuCl in pump and probe experiments

We study the dispersion and the absorption changes of CuCl under high excitation conditions in two-beam experiments with parallel and crossed linear polarizations of both beams. The induced optical non linearities are shown to depend sensitively on the presence of interactions between the degenerate transverse exciton states.     

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.