Nodal quasiparticle meltdown in ultra-high resolution pump-probe angle-resolved photoemission

TL;DR

This study uses ultra-high resolution pump-probe ARPES to reveal that nodal quasiparticles in high-$T_c$ cuprates are affected by superconductivity, showing suppressed spectral weight post-excitation, which challenges the traditional view of their independence.

Contribution

It demonstrates a direct link between nodal quasiparticles and superconductivity, revealing their suppression and recovery dynamics using advanced time-resolved ARPES.

Findings

Nodal quasiparticle spectral weight is suppressed after laser excitation.

Suppression of nodal quasiparticles is enhanced in the superconducting state.

Results challenge the view that nodal excitations are unaffected by superconductivity.

Abstract

High-$T_c$ cuprate superconductors are characterized by a strong momentum-dependent anisotropy between the low energy excitations along the Brillouin zone diagonal (nodal direction) and those along the Brillouin zone face (antinodal direction). Most obvious is the d-wave superconducting gap, with the largest magnitude found in the antinodal direction and no gap in the nodal direction. Additionally, while antinodal quasiparticle excitations appear only below $T_c$, superconductivity is thought to be indifferent to nodal excitations as they are regarded robust and insensitive to $T_c$. Here we reveal an unexpected tie between nodal quasiparticles and superconductivity using high resolution time- and angle-resolved photoemission on optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. We observe a suppression of the nodal quasiparticle spectral weight following pump laser excitation and measure its recovery dynamics. This suppression is dramatically enhanced in the superconducting state. These results reduce the nodal-antinodal dichotomy and challenge the conventional view of nodal excitation neutrality in superconductivity.