Superconductivity versus phase separation, stripes, and checkerboard ordering: A two-dimensional Monte Carlo study

Abstract

Using Monte Carlo techniques, we study a simple model which exhibits a competition between superconductivity and other types of order in two dimensions. The model is a site-diluted XY model, in which the XY spins are mobile, and also experience a repulsive interaction extending to one, two, or many shells of neighbors. Depending on the strength and range of the repulsion and spin concentration, the spins arrange themselves into a remarkable variety of patterns at low temperatures T, including phase separation, checkerboard order, and straight or labyrinthine patterns of stripes, which sometimes show hints of nematic or smectic order. This pattern formation profoundly affects the superfluid density γ. Phase separation tends to enhance γ, checkerboard order suppresses it, and stripe formation increases the component of γ parallel to the stripes and reduces the perpendicular one. We verify that γ(T=0) is proportional to the effective conductance of a random conductance network whose conductances equal the couplings of the XY system. Possible connections between the model and real materials, such as single high-Tc cuprate layers, are briefly discussed.

Source-reported materials — not catalogue approval

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