On exotic orders in strongly correlated systems

摘要: The key to understanding interacting many-body systems at low temperatures is often identify their dominant ordering pattern. Though some types of order seem extremely robust and prevalent in nature, those which lie the frontier our are result subtle competition between interactions, hence can be delicate difficult identify. This lead intricate phase diagrams, as varying parameters favors different orders. They also exhibit surprising emergent properties, including deconfined gauge fields or topological not present microscopic model. Understanding nature scope these novel orders one tools mastering vast practical intellectual potential low-temperature correlated materials. In this thesis, we explore orders, both classical quantum, emerge several strongly temperature. Chapter 2, investigate magnetic antiferromagnets on a class dilutions face-centered cubic lattice. Exploiting fact that Hamiltonian particular stacking triangular planes, find 120 degree for Heisenberg andXY magnets, an entropically driven 3-sublattice Ising case. 3, propose (topologically ordered) gapless spin liquid state highly frustrated pyrochlore antiferromagnet. We energetically favored symmetric using large Nf expansion, arguments its stability fluctuations about infinite mean-field state. 4 explains