Date of Award
12-2007
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Legacy Department
Theoretical Physics
Committee Chair/Advisor
Marinescu, Catalina
Committee Member
Manson , Joseph R
Committee Member
Ke , Pu-Chun
Committee Member
Sosolik , Chad
Abstract
We discuss the existence of spin instabilities and of possible ground states with broken spin symmetry in the presence of a tilted magnetic field for several semiconductor heterostructures. In each instance, the fundamental premise of our study is the existence of a spin degeneracy, controlled by tuning various experimentally controllable parameters, that permits the apparition of spin-flip processes driven entirely by the many-body Coulomb interaction. If in the case of a single quantum well, the spin instabilities trigger an abrupt paramagnetic to ferromagnetic phase transition, we demonstrate that in superlattices, at low temperatures, a stable spin density wave ($SDW$) ground state is supported for certain system parameters that allow a substantial overlap of the opposite spin interbands when the electron-electron interaction is considered within the Hartree-Fock approximation. In our study, we consider two different types of superlattices that present both spin instabilities that involve electrons from different Landau levels, as well as from the same, lowest Landau level. In each case, we solve the SDW gap equation numerically through an iterative procedure and study the dependence of the solution on the relevant system parameters. Our numerical estimates indicate that in the SDW ground state, the systems present a sizable spin polarization that is entirely controllable by external means, generating possible spintronics applications.
Recommended Citation
Zheng, Liqiu, "Spin Density Wave Phases in Semiconductor Superlattice" (2007). All Dissertations. 168.
https://tigerprints.clemson.edu/all_dissertations/168