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Free keywords:
magnetic excitation; y-based cuprates; fermi surface
Abstract:
A pronounced xy-anisotropy was observed in recent neutron scattering experiments for magnetic excitations in untwinned YBa2-Cu3O6+y (YBCO). The small anisotropy of the bare band structure due to the orthorhombic crystal symmetry seems to be enhanced by correlation effects. A natural possibility is that the system is close to a Pomeranchuk instability associated with a d-wave Fermi surface deformation (dFSD). We investigate this possibility in the bilayer t-J model within a self-consistent slave-boson mean-field theory. We show that the dFSD correlations drive a pronounced xy-anisotropy of magnetic excitations at low doping and at relatively high temperatures, providing a scenario for the observed xy-anisotropy in optimally doped as well as underdoped YBCO, including the pseudogap phase. (c) 2007 Elsevier B.V. All rights reserved.
