Intrinsic Tunneling Spectra of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ near Optimal Doping

TL;DR

This study presents temperature-dependent tunneling spectra of near optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+eta}$, revealing a pseudogap up to 230 K and insights into electron-boson interactions through a d-wave Eliashberg analysis.

Contribution

It provides stable, high-resolution tunneling spectra near optimal doping and identifies two pseudogap phases, advancing understanding of high-temperature superconductivity mechanisms.

Findings

Pseudogap persists up to 230 K.

Spectra fit well with electron coupling to magnetic resonance mode.

Evidence of two distinct pseudogap phases above $T_c$.

Abstract

We report tunneling spectra of near optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ intrinsic Josephson junctions with area of 0.09 $\mu$m$^2$, which avoid some fundamental difficulties in the previous tunneling experiments and allow a stable temperature-dependent measurement. A d-wave Eliashberg analysis shows that the spectrum at 4.2 K can be well fitted by considering electron couplings to a bosonic magnetic resonance mode and a broad high-energy continuum. Above $T_c$, the spectra show a clear pseudogap that persists up to 230 K, and a crossover can be seen indicating two different pseudogap phases existing above $T_c$. The intrinsic electron tunneling nature is discussed in the analysis.