Field theoretical approach to metamagnetic superconductivity and solitons

Quantum field theory is applied to the study of condensed matter physics. In field theory, ordered states are created because of the spontaneous breakdown of symmetry and classical extended objects are obtained by the use of the boson tranformation method. The application to the study of metamagnetic superconductors and solitons is then presented.;In the study of metamagnetic superconductors, a four-sublattice Ginsburg and Landau model with fourfold symmetry is considered. The phase diagrams and the magnetization curves for the normal state are obtained. The superconducting state of the four sublattices metamagnetic model is then considered and the boson transformation method is applied in order to study the mixed state with the appearance of vortices. The study is complicated by the many possible magnetic configurations. Many different shapes of H;Finally, the study of the statistic of renormalized solitons is presented. The N solitons sector is considered and the free energy for the system is obtained. The calculation gives a clear picture of how the temperature corrections from the renormalized masses affect the free energy and how the stable soliton profiles can be preserved.