Gap like structure in a nonsuperconducting layered oxycarbonate Bi$_{2+x}$Sr$_{4-x}$Cu$_2$CO$_3$O$_{8+\delta}$ single crystal

TL;DR

This study investigates the in-plane tunneling conductance in a nonsuperconducting layered oxycarbonate, revealing a small pseudogap that may be related to the emergence of superconductivity in cuprates.

Contribution

It provides evidence for a pseudogap in nonsuperconducting cuprates without superconductivity-related phenomena, challenging existing theories.

Findings

Existence of a pseudogap in nonsuperconducting cuprates

No evidence of local incoherent pairs

Pseudogap may be a precursor to superconductivity

Abstract

The magnetic field and temperature dependence of the in-plane tunneling conductance $dI/dV(V)$ in high-quality nonsuperconducting (down to 10 mK) layered oxycarbonate Bi$_{2+x}$Sr$_{4-x}$Cu$_2$CO$_3$O$_{8+\delta}$ single crystals has been investigated using break junctions. Combining measurements of the in-plane magnetoresistivity $\rho_{ab}(T,H)$ and the magnetotunneling, we present evidence for the existence of a small "pseudogap" in a nonsuperconducting cuprate, without local incoherent pairs or any correlation phenomena associated with superconductivity. We are unable to distinguish if such a "pseudogap" is totally unrelated to superconductivity or if its existence is a necessary condition for the subsequent occurrence of superconductivity with increasing carrier density in the sample.