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We have studied high-temperature superconducting cuprates samples
throughout the doping-temperature phase diagram. We find that the low energy excitations of these systems have
a surprising, universal character at low doping. We have developed a procedure to extract the angular dependence of
the excitations near the node of the d-wave order parameter from scanning tunneling spectroscopy (STS) data.
Using this procedure, we show that the universal character of low energy excitations stems from a universal angular
dependence of the gap as a function of angle near the nodes.
We find that the reduction in Tc with reduced doping for underdoped samples is correlated with a
reduction in the angular range over which we find universal nodal excitations. By contrast, reduction in Tc with
increased doping for overdoped samples is correlated with a collapse of the universal nodal behavior and a nodal gap
that reduces in strength.
Published in Science Express: Report
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Joseph Henry Laboratories of Physics
Department of Physics
Jadwin Hall
Princeton University
Princeton, NJ 08544
Tel: 609.258.4390
FAX: 609.258.1006
Lab phone/fax: 609.258.9517
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