Coordination of the energy and temperature scales of pairing across the doping phase diagram of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$

TL;DR

This study uses advanced photoelectron spectroscopy to measure pairing and self-energy processes in Bi2212 across various doping levels, revealing that pairing persists above T_c and is strongly coupled, independent of pseudogap effects.

Contribution

It introduces a new spectroscopy method to measure pairing and self-energy across doping levels, showing pairing extends above T_c and is universally strongly coupled in Bi2212.

Findings

Pairing extends above T_c to T_{Pair}

Strong coupling ratio 2Δ /k_B T_{Pair} ≈ 6

Pairing is independent of pseudogap effects

Abstract

Using a new variant of photoelectron spectroscopy, we measure the homogeneous near-nodal pairing ($\Delta$) and pair-breaking self-energy ($\Gamma_S$) processes for a wide range of doping levels of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. For all samples we find that the pairing extends above the superconducting transition T$_c$ to a scale T$_{Pair}$ that is distinct from the antinodal pseudogap scale T$^*$ and near but slightly above T$_c$. We find that $\Delta$ and T$_{Pair}$ are related with a strong coupling ratio 2$\Delta$ /k$_B$T$_{Pair}\approx6$ across the entire doping phase diagram, i.e. independent of the effects of antinodal pseudogaps or charge-density waves.