Two energy scales and two distinct quasiparticle dynamics in the superconducting state of underdoped

Abstract

The superconducting temperature Tc of hole-doped high-temperature superconductors has a dome-like shape as a function of hole concentration, with a maximum Tc at ‘optimal’ doping. On the underdoped side, the superconducting state is often described in terms of one energy scale, associated with the maximum of the d-wave gap (at the antinodes), which increases as the doping decreases. Here, we report electronic Raman scattering experiments that show a second energy scale in the gap function: the slope of the gap at the nodes, which decreases with decreasing doping. Our measurements also reveal two distinct quasiparticle dynamics; electronic coherence persists down to low doping levels at the nodes, whereas antinodal quasiparticles become incoherent. Using a sum-rule, we find that the low-frequency Raman response and the temperature dependence of the superfluid density, both controlled by nodal excitations, behave in a qualitatively similar manner with doping variation.

Cite this article

Le Tacon, M., Sacuto, A., Georges, A. et al. Two energy scales and two distinct quasiparticle dynamics in the superconducting state of underdoped cuprates. Nature Phys 2, 537–543 (2006). https://doi.org/10.1038/nphys362

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