Theoretical Studies of Condensed Matter Systems with Multiple Broken Symmetries
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- Institutt for fysikk 
This thesis consist of six research articles in the field of condensed matter physics. Three of the articles concern two superfluid components interacting through an Andreev–Bashkin term. In article I, we present a preemptive scenario where we aim at understanding the role of the topological defects in the various phase transitions. We present vortex-matter based analytical arguments, which allow us to describe the phase diagram. The analytical arguments are backed up by large scale Monte Carlo computation. Articles II and III consider the same system subjected to rotation. In article II, we consider a repulsive intercomponent interaction between co-directed vortex segments, while in article III the interaction is attractive. We study different lattice orderings and find e.g. a “hidden” lattice ordering and a vortex supersolid. Three articles are related to superconductivity. In article IV, we derive a Ginzburg–Landau free energy for a ferromagnetic p-wave superconductor, from a microscopic Hamiltonian.We find analytical expressions for the coefficients. Specifically we find that coexistence of ferromagnetism and superconductivity depends on the sign of the energy gradient of the DOS at Fermi level. Articles V and VI consider a model proposed to describe the transition from the Strange Metal phase to the Pseudogap phase, in the high-Tc cuprates. We perform a Monte Carlo study of the ordering of loop-currents, and find that there is no signal in the specific heat, while there is a divergence in the magnetic susceptibility.