J.-P. Jay-Gerin

The electron mobility and the static dielectric constant of Cd3As2 at 4.2 K

Abstract The ionized-impurity mobility of Cd 3 As 2 at 4.2 K with carrier concentration lying in the range 10 18 –10 19 cm −3 has been calculated taking into account the inverted HgTe-type energy band structure of this material. A comparison of the results with experimental mobility data leads to a static dielectric constant of ϵ 0 = 36. This value represents a lower limit since any compensation effects would increase the fitted estimate of ϵ 0 .

Electron mobility in Cd3−xZnxAs2 alloys

Abstract Theoretical calculations have been made of the electron mobility of Cd 3− x Zn x As 2 alloys with x ≲ 1.5 at 77 and 300 K. The observed variation of carrier concentration with increasing zinc composition is attributed to compensation effects which are assumed to vary linearly with x . The calculations have taken into account the HgTe-like energy-band structure which is applicable in one range of alloy composition and the InSb-like energy-band structure which is applicable in another. Scattering due to charged centers, acoustic phonons, and optical phonons have been considered. It is found that the latter dominates at 300 K whereas the former is most important at 77 K. An excellent agreement with the available experimental data is obtained. In particular, the observed maximum in the room-temperature mobility curve near x = 0.25 is well accounted for.

The energy-band parameters of cadmium arsenide and their variation with temperature and pressure☆

Abstract Using Kanes model for an HgTe-type inverted energy band structure along with available transport and optical data, various band parameters of Cd 3 As 2 have been obtained at room and at low temperatures. Theoretical estimates of the variation of the energy gap at Γ as a function of temperature and pressure have also been obtained. These are found to be consistent with our band model and with our analysis of existing temperature and pressure data.

Low-temperature specific heats of ZrSe3 and ZrS3

Abstract The specific heats of the semiconducting compounds ZrSe3 and ZrS3 have been measured in the temperature range between 8 and 200 K. At the lowest values of T, the ZrSe3 measurements can be analyzed in terms of the familiar Debye T3 law yielding a characteristic Debye temperature at absolute zero θD(0) = 110 ± 2 K in satisfactory agreement with the value extracted from the available experimental sound velocities. In contrast, the low-temperature ZrS3 measurements do not behave according to the Debye law. This is interpreted as resulting from a strong mixing of low-lying optical modes with the acoustical branches, and reflects a more pronounced one-dimensional character of ZrS3 compared to ZrSe3.

On the determination of the electron g-factor in a degenerate semiconductor

Abstract We have derived a simple formula for determining the electronic Landeg-factor in a degenerate semiconductor directly from the experimental observation of spin-split Shubnikov-de Haas-type oscillations.

A note on the study of the thermomagnetic effects in graphite at low temperatures

Abstract The present paper is devoted to the study of the thermomagnetic effects, namely the thermoelectric power, S ( H ), and the Nernst-Ettingshausen coefficient, A NE ( H ), in graphite at low temperatures and in the presence of small magnetic fields ( H ⪅ 15 kG). It is shown that the theory developed by Jay-Gerin and Maynard and by Jay-Gerin, on the basis of the phonon-drag effect in graphite, predicts a numerical estimate of S ( H ) and A NE ( H ) which is in good agreement with the recent, though preliminary, experimental results of Takezawa, Mangez, Hewes, Dresselhaus and Tsuzuku. The need for a complete experimental analysis of all of the thermo-galvanomagnetic transport coefficients, taken on the same sample of graphite, over a wide range of magnetic fields and temperatures, is emphasized.

The filled band contribution to the low temperature magnetization of graphite in strong magnetic fields

Abstract It is shown that the contribution of filled band electrons to the low-temperature magnetization of graphite explains remarkably well the recently observed high-field diamagnetism of graphite, refuting a previous theoretical prediction that graphite might become paramagnetic in the ultra-quantum limit.

Specific heat of pure graphite in the ultra-quantum limit region

Abstract We calculate the electronic specific heat of pure graphite in the ultraquantum limit region for fields between 60 and 200 kG, at very low temperatures, using the Slonczewski-Weiss band model with values of the energy-band parameters which are in agreement with recent magneto-replection experiments. The effect of trigonal warping of the Fermi surfaces associated with the parameter γ 3 is neglected in the calculation. Our results show that, for most of the range of fields considered, the electronic specific heat C is very nearly proportional to both the magnetic field strength H and the temperature T , according to the relation C ≈ α HT with a coefficient α of about 0.091 μJ/g-at. K 2 kG. The results also indicate that, at the upper end of the magnetic field range, the C ( H ) curves, at a given T , depart slightly and progressively from linearity with increasing H , essentially as a result of the variation of the Fermi energy with magnetic field.

Thermoelectric Power of TiSe2−xSx Mixed Crystals

We present thermoelectric power (TEP) measurements as a function of temperature in the range 7–450 K of TiSe2−xSx mixed crystals for x =.1, .5, .75, 1 and 1.25. The semimetallic 1T − TiSe2 is known to undergo an antiferrodistortive phase transition below 200 K which is accompanied by some peculiar features in transport properties. Especially, the TEP exhibits a pronounced negative dip around 150 K. Similarly to that TiSe2 behaviour, mixed samples presenting the superlattice state are also observed to possess the dip. In contrast, the TEP of the non-transforming crystals varies monotonously with temperature. We interpret the occurrence of the dip in transforming crystals on the basis of a phonon-drag effect associated with the transition. A previously proposed antiferroelectric mechanism is thus concluded to be irrele-vant to the TiSe2 problem as it would imply strong intrinsic anharmonic effects and reduction of dragging effect. Instead, our analysis favours electron-phonon interpocket coupling as the driving mechanism. However, opposite to the transitions occurring in metallic dichalcogenides, the “nesting conditions” are not thought to be essential in the present case as the dip position does not shift upon mixing. Finally, an evaluation is provided for the non-renormalized energy of the softening phonon L 1 − (1).