Transport properties of diluted magnetic semiconductors: Dynamical mean field theory and Boltzmann theory

TL;DR

This paper investigates the transport properties of diluted magnetic semiconductors using dynamical mean field theory and Boltzmann transport theory, revealing how parameters like temperature and doping influence resistivity and magnetic behavior.

Contribution

It combines DMFT and Boltzmann theory to analyze DMS transport, providing a detailed understanding of the effects of carrier-spin coupling and impurity scattering.

Findings

Resistivity depends on temperature, doping, and carrier-spin coupling.

Spin-disorder scattering and bound states influence transport.

Metallic behavior below Curie temperature explained by screening and spin polarization.

Abstract

The transport properties of diluted magnetic semiconductors (DMS) are calculated using dynamical mean field theory (DMFT) and Boltzmann transport theory. Within DMFT we study the density of states and the dc-resistivity, which are strongly parameter dependent such as temperature, doping, density of the carriers, and the strength of the carrier-local impurity spin exchange coupling. Characteristic qualitative features are found distinguishing weak, intermediate, and strong carrier-spin coupling and allowing quantitative determination of important parameters defining the underlying ferromagnetic mechanism. We find that spin-disorder scattering, formation of bound state, and the population of the minority spin band are all operational in DMFT in different parameter range. We also develop a complementary Boltzmann transport theory for scattering by screened ionized impurities. The difference in the screening properties between paramagnetic ($T>T_c$) and ferromagnetic ($T<T_c$) states gives rise to the temperature dependence (increase or decrease) of resistivity, depending on the carrier density, as the system goes from the paramagnetic phase to the ferromagnetic phase. The metallic behavior below $T_c$ for optimally doped DMS samples can be explained in the Boltzmann theory by temperature dependent screening and thermal change of carrier spin polarization.