Many-body effects in two-dimensional electronic systems

Sudhakar Yarlagadda, Purdue University

Abstract

In this Thesis we have set up a self-consistent scheme to calculate the effective mass m*, the modified Lande factor g*, and the spin susceptibility $\chi\sb{\rm S}$ of an electron gas. Our investigations were carried out in both quasi-two dimensions and strictly two dimensions. Quasi-two dimensional systems are realized in semiconductor inversion layers, semiconductor heterojunctions, superlattices, etc. In our analysis we have attempted to take into account the vertex corrections associated with both charge and spin fluctuations through the use of many-body local fields. The final expressions for m*, g*, and $\chi\sb{\rm S}$ were obtained by making use of Landau Fermi liquid theory. Within this framework, we used two different approaches to obtain the desired physical quantities. The first approach involved the derivation of an effective quasiparticle hamiltonian for an electron gas with arbitrary polarization. The second approach requires a precise knowledge of the total energy of the system as a functional of the occupation numbers of spin up and spin down electrons. The total energy was obtained using the coupling constant algorithm. We find that partially accounting for the many-body local field corrections leads to erroneous results. Our theory is in reasonable agreement with the existing experimental data. We have also examined the problem of spin susceptibility in a strictly two dimensional electron gas. We find that the Hartree-Fock approximation and its generalizations are not adequate to fully take into account many-body effects associated with charge- and spin-density fluctuations.

Degree

Ph.D.

Advisors

Giuliani, Purdue University.

Subject Area

Condensation

COinS