Dynamics of correlation-frozen antinodal quasiparticles in superconducting cuprates

TL;DR

This study uses ultrafast EUV photoemission to investigate the dynamics of antinodal quasiparticles in high-temperature superconducting cuprates, revealing transient metallic states and momentum-dependent electron behavior crucial for understanding superconductivity.

Contribution

It provides the first direct observation of ultrafast antinodal quasiparticle dynamics and transient metallicity, linking low- and high-energy electronic scales in cuprates.

Findings

Transient antinodal metallic states emerge after photoexcitation.

Nodal quasiparticles behave like in a conventional metal.

Correlation-driven electron freezing is key to high-$T_c$ superconductivity.

Abstract

Many puzzling properties of high-$T_c$ superconducting (HTSC) copper oxides have deep roots in the nature of the antinodal quasiparticles, the elementary excitations with wavevector parallel to the Cu-O bonds. These electronic states are most affected by the onset of antiferromagnetic correlations and charge instabilities and they host the maximum of the anisotropic superconducting gap and pseudogap. In this work, we use time-resolved extreme-ultra-violet (EUV) photoemission with proper photon energy (18 eV) and time-resolution (50 fs) to disclose the ultrafast dynamics of the antinodal states in a prototypical HTSC cuprate. After photoinducing a non-thermal charge redistribution within the Cu and O orbitals, we reveal a dramatic momentum-space differentiation of the transient electron dynamics. While the nodal quasi-particle distribution is heated up as in a conventional metal, new quasiparticle states transiently emerge at the antinodes, similarly to what is expected for a photoexcited Mott insulator, where the frozen charges can be released by an impulsive excitation. This transient antinodal metallicity is mapped into the dynamics of the O-2$p$ bands thus directly demonstrating the intertwining between the low- and high-energy scales that is typical of correlated materials. Our results suggest that the correlation-driven freezing of the electrons moving along the Cu-O bonds, analogous to the Mott localization mechanism, constitutes the starting point for any model of high-$T_c$ superconductivity and other exotic phases of HTSC cuprates.