Quantum Transport Effects Research Articles

Some aspects of classical and quantum transport in thin films of cadmium arsenide

We investigated the classical transport properties (the Hall effect and the Hall mobility) and the quantum transport (the Shubnikov-de Haas (SdH) effect) in thin crystalline and amorphous films of Cd 3As 2. The measurements were performed in high magnetic fields (up to 35 T) at 4.2 K. We found from the SdH effect that the crystalline films are slightly anisotropic, indicating that the investigated structures have a texture, whereas the amorphous films appear to be completely isotropic. Comparison of the Hall data with the SdH data showed some discrepancies between the electron concentrations and mobilities determined by the two methods. The experimental results obtained are discussed on the basis of existing theoretical models for electronic transport in semiconducting thin films.

Diluted magnetic semiconductors: An interface of semiconductor physics and magnetism (invited)

This paper reviews the electrical, magnetic, and optical properties of diluted magnetic semiconductors (sometimes also referred to as ‘‘semimagnetic’’ semiconductors). These materials are ternary semiconductor alloys whose lattice is made up in part of substitutional magnetic ions. Cd1−xMnxTe and Hg1−xMnxTe are examples of such systems. As semiconductors, these alloys display interesting and important properties, such as the variation of the energy gap and of effective mass with composition. They also exhibit magnetic properties which are interesting in their own right, e.g., a low temperature spin glass transition and magnon excitations. Most importantly, however, the presence of substitutional magnetic ions in these alloys leads to spin–spin exchange interaction between the localized magnetic moments and the band electrons. This in turn has rather important consequences on band structure and on donor and acceptor states, leading to dramatic effects in quantum transport, impurity conduction, and magneto-optics. Specifically, the presence of exchange interaction results in extremely large and temperature dependent g-factors of electrons and holes; in gigantic values of Faraday rotation; in anomalously large negative magnetoresistance; and in the formation of the bound magnetic polaron.

Quantum transport effects in cadmium arsenide, effective mass tensor and band structure

Shubnikov-De Haas observations in n-type cadmium arsenide are reported, n = 2.6 x 10 18 cm -3 and application is made to band structure determination. A single revolution ellipsoid round c-axis is found with m ∗ |/m o = 0.043

Quantum theory of transverse galvano-magnetic phenomena

A quantum theory of electrical conduction in crosfsed electric and magnetic fields is given for the limit of very weak scattering. A density matrix formulation of the problem is used, and an arbitrary scattering mechanism is considered. The theory is found to be completely equivalent to theories given earlier by Titeica and by Davydov and Pomeranchuk. Formulae are given for the resistivity in the quantum limit for both longitudinal and transverse orientations of electric field, for degenerate and non-degenerate statistics, and for several different scattering mechanisms. The oscillatory conductivity is calculated for acoustical and ionized-impurity scattering mechanisms. Formulae obtained for the quantum transport effects are in disagreement with the formulae of Lifshitz and of Argyres. The discrepancy is attributed to unwarranted approximations in those authors' treatments of scattering.