title: Quantum criticality: competing ground states in low dimensions
abstract: Small changes in an external parameter can often lead to dramatic qualitative changes in the lowest energy quantum mechanical ground state of a correlated electron system. In anisotropic crystals, such as the high-temperature superconductors where electron motion occurs primarily on a two-dimensional square lattice, the quantum critical point between two such lowest energy states has nontrivial emergent excitations that control the physics over a significant portion of the phase diagram. Nonzero temperature dynamic properties near quantum critical points are described, using simple theoretical models. Possible quantum phases and transitions in the two-dimensional electron gas on a square lattice are discussed.
authors.affiliation: Department of Physics, Yale University, Post Office Box 208120, New Haven, CT 06520-8120, USA.
authors.initials: S
authors.lastname: Sachdev