Slow fracton modes in antiferromagnetic correlations of high-Tc superconductors

Mladen Prester

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Slow fracton modes in antiferromagnetic correlations of high-Tc superconductors

Mladen Prester

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Abstract

In cuprate superconductors superconductivity develops as a unique cross over between the two extremal phases characterizing these compounds. The extremal phases are known to be an antiferromagnetic (AF) Mott insulator one, on one side, and a non-superconducting itinerant metal on the other. Numerous inelastic neutron scattering studies on underdoped samples shows most directly that the static AF order of the parent phase does not disappear by doping but transforms in such a way that at least fluctuating and local AF order persists, coexisting with superconductivity. Structurally, the model of stripe-type correlations accounts for the coexistence while its genuine dynamics might hide the most interesting physics of cuprates, including the pairing mechanism. Indeed, there is an impressive accumulation of knowledge in favour of AF correlations underlying the pairing. Some crucial properties of these correlations have been recently pointed out: they should involve small velocity collective modes of the wave vector identical to that of static AF order while their energy scale (<50 meV) should be rather low compared with any other involved. In this work we show on phenomenological ground that the very concept of a disordered AF phase interpenetrated with non-magnetic boundaries comprises, irrespective of structural details of stripe order, the dynamical ingredients (fractons) which may be important for pairing. The model elaborated below introduces a new energy scale (10-50 meV) associated with slow (or almost localized) and well-defined AF excitations, interpreting simultaneously most of the neutron scattering results in a consistent and a natural way.

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Mladen Prester. 2001-07-30. Slow fracton modes in antiferromagnetic correlations of high-Tc superconductors. https://arxiv.org/abs/cond-mat/9911458

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