Non-conservation of density of states in y: Coexistence of pseudogap and superconducting gap
Department of Physics and Astronomy, University of Kentucky
Lexington, KY 40506-0055, USA
Accepted: 25 March 2002
The tunneling spectra obtained within the (a,b)-plane of y (Bi2212) for temperatures below and above the critical temperature are analyzed. We find that the tunneling conductance spectra for the underdoped compound in the superconducting state do not follow the conservation of states rule. There is a consistent loss of states for the underdoped Bi2212 implying an underlying depression in the density of states (DOS) and hence the pseudogap near the Fermi energy . Such an underlying depression can also explain the peak-dip-hump structure observed in the spectra. Furthermore, the conservation of states is recovered and the dip-hump structure disappears after normalizing the low-temperature spectra with that of the normal state. We argue that this is a direct evidence for the coexistence of a pseudogap with the superconducting gap.
PACS: 74.50.+r – Proximity effects, weak links, tunneling phenomena, and Josephson effects / 74.25.Jb – Electronic structure / 74.25.-q – General properties; correlations between physical properties in normal and superconducting states
© EDP Sciences, 2002