Satoshi Okamoto, Nobuo Furukawa
Using dynamical-mean-field theory for clusters, we study the two-dimensional Hubbard model in which electrons are coupled with the orthorhombic lattice distortions through the modulation in the hopping matrix. Instability towards spontaneous symmetry breaking from a tetragonal symmetric phase to an orthorhombic distorted phase is examined as a function of doping and interaction strength. Moderate instability is observed near the van Hove filling for all the interaction strengths studied. Additionally, a very strong instability is found in the underdoped pseudogap regime when the interaction strength is large enough to yield the Mott insulating phase at half filling. We discuss the implications of our results to the four-fold symmetry breaking reported in systems where the underlying crystal does not have any structural anisotropy.
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http://arxiv.org/abs/1205.6150
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