Distinct doping dependences of the pseudogap and superconducting gap La$_{2-x}$Sr$_{x}$CuO$_4$ cuprate superconductors

TL;DR

This study reveals that in La$_{2-x}$Sr$_{x}$CuO$_4$ cuprates, the pseudogap and superconducting gap depend differently on doping levels, with the pseudogap increasing as doping decreases, while the superconducting gap remains small.

Contribution

It provides experimental evidence that the pseudogap and superconducting gap have distinct doping dependences and spatial origins in cuprate superconductors.

Findings

Pseudogap magnitude and onset temperature increase with decreasing doping.

Superconducting gap remains small as doping decreases.

Pseudogap opens around ($\pi$, 0), while the superconducting gap appears on the Fermi arc.

Abstract

We have performed a temperature-dependent angle-integrated photoemission study of lightly-doped to heavily-overdoped La$_{2-x}$Sr$_{x}$CuO$_4$ and oxygen-doped La$_2$CuO$_{4.10}$. We found that both the magnitude $\Delta$* of the (small) pseudogap and the temperature \textit{T}* at which the pseudogap is opened increases with decreasing hole concentration, consistent with previous studies. On the other hand, the superconducting gap $\Delta_{sc}$ was found to remain small for decreasing hole concentration. The results can be explained if the superconducting gap opens only on the Fermi arc around the nodal (0,0)-($\pi,\pi$) direction while the pseudogap opens around $\sim$($\pi$, 0).