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Non-conservation of Density of States in Bi$_2$Sr$_2$CaCu$_2$O$_y$: Coexistence of Pseudogap and Superconducting gap

Anjan K. Gupta·K. -W. Ng
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Abstract

The tunneling spectra obtained within the ab-plane of Bi$_2$Sr$_2$CaCu$_2$O$_y$ (Bi2212) for temperatures below and above the critical temperature (T$_c$) 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 (E$_F$). 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.

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Anjan K. Gupta, K. -W. Ng. 2002-02-25. Non-conservation of Density of States in Bi$_2$Sr$_2$CaCu$_2$O$_y$: Coexistence of Pseudogap and Superconducting gap. https://doi.org/10.1209/epl%2Fi2002-00456-2

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