Quantum-Monte-Carlo Studies of One- and Two-Dimensional Hubbard Models
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Despite tremendous efforts, the question of whether two-dimensional repulsive Hubbard-type models have a superconducting phase, i. e. off-diagonal long-range order (ODLRO), is still unresolved. At present there is not even consensus on the symmetry channel in which superconductivity might occur! Therefore we present and numerically analyze two methods to detect superconductivity without any prior knowledge about the nature of the condensate and, in particular, of the symmetry of the underlying pair-pair correlation functions: flux quantization and the temperature derivative of the superfluid density. Both methods rely on generalizations of QMC algorithms to incorporate magnetic fields. Our data confirm the Kosterlitz-Thouless transition in the attractive case and rule out superconductivity in the quarter-filled repulsive one-band Hubbard model.
KeywordsHubbard Model Flux Quantization Luttinger Liquid Superfluid Density Large Lattice Size
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