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Central peak in the pseudogap of high TC superconductors

A detailed theoretical description is provided of the narrow low-energy peak in the ARPES response of superconducting optimally doped and weakly underdoped BSCCO near the van Hove point. The pseudogap is taken to be due to electronparamagnon scattering. The narrow peak is antiadiabatic: it consists of electrons which are so slow that the scattering is not effective in suppressing their spectral strength. We find two temperature regimes for the pseudogap. The low-temperature one is relevant for experiment in BSCCO, where the paramagnon band-edge is much higher than the temperature. The hightemperature regime occurs when the band-edge is lower than the temperature. It is characterized by hot spots when the band-edge is finite, and develops a macroscopic antiferromagnetic potential when it vanishes. We argue that it is relevant for the electron-doped high-Tc compounds. Our work gives a connection between the simultaneous appearance of a magnetic resonance and a narrow low-energy feature in ARPES at the superconducting transition in BSCCO. In the model, both can be obtained by switching the paramagnon damping from supercritical to subcritical, without even including the superconducting correlations explicitly. The leading edge scale of the narrow peak is controlled by the chemical potential and is incidental to the pseudogap mechanism, whose physical scale is given by the high-energy ‘ hump.’

ARPES; pseudogap; high-Tc; superconductivity

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