Spin in fractional quantum Hall systems [Elektronische Ressource] / Karel Výborný

Spin in fractional quantum Hall systemsKarel Vyb ornyAbstractThe present numerical study concerns fractional quantum Hall systems at lling factors2 2 = and . By means of the exact diagonalization of systems with few electrons in a3 5rectangle with periodic boundary conditions we investigate the many{body ground statesand low{lying excited states. Homogeneous systems as well as systems with some specialforms of inhomogeneities are considered. Particular emphasis is put on the spin degree offreedom and on possible analogies to Ising ferromagnets.The core of the work is set up into four Chapters: experimental results and especially those2 2hinting at ferromagnetism at = ; are reviewed and a wider theoretical introduction is3 5given. In another two Chapters, rst the homogeneous systems are examined and then the2capability of the = systems to form spin structures under the in uence of magnetic3inhomogeneities is investigated.For homogeneous systems we rst examine the inner structure of the well{established spinpolarized and spin singlet incompressible ground states. Based on this study, we propose2a new interpretation of the singlet ground state at lling . Links to composite fermion3theories are mentioned and among them especially those which may seem counterintuitiveat the rst look. Further, a half{polarized state is found which could become the absolute2ground state at = in a narrow range of electron density.