Pseudogap, Superconducting Gap, and Fermi Arcs in Underdoped Cuprate Superconductors

TL;DR

This study reveals a close relationship between the pseudogap and superconducting gap in underdoped cuprates, showing that their doping dependencies are similar and linked through specific heat measurements, supporting RVB theory.

Contribution

It provides experimental evidence connecting the pseudogap, superconducting gap, and Fermi arcs, supporting the SU(2) slave boson theory in cuprate superconductors.

Findings

The nodal slope of the superconducting gap has a doping dependence similar to the pseudogap temperature.

The maximum quasiparticle gap is close to the pseudogap temperature.

The relation T_c ≈ β v_Δ γ_n(0) links critical temperature to gap slope and residual Fermi arc size.

Abstract

Through the measurements of magnetic field dependence of specific heat in $La_{2-x}Sr_xCuO_4$ in zero temperature limit, we find that the nodal slope $v_\Delta$ of the superconducting gap has a very similar doping dependence of the pseudogap temperature $T^*$ or value $\Delta_p$. Meanwhile the maximum quasiparticle gap derived from $v_\Delta$ is quite close to $T^*$. Both indicate a close relationship between the pseudogap and superconductivity. It is also found that $T_c \approx \beta v_\Delta \gamma_n(0)$, where $\gamma_n(0)$ is the extracted zero temperature value of the normal state specific heat coefficient which is proportional to the size of the residual Fermi arc $k_{arc}$. These observations mimic the key predictions of the SU(2) slave boson theory based on the general resonating-valence-bond (RVB) picture.