Quasiparticles dynamics in high-temperature superconductors far from equilibrium: an indication of pairing amplitude without phase coherence

TL;DR

This study uses time-resolved photoelectron spectroscopy to reveal that high-temperature superconductors exhibit a finite pairing amplitude without phase coherence under strong excitation, challenging traditional understanding of superconductivity.

Contribution

It demonstrates the existence of a regime with pairing amplitude but no phase coherence in high-temperature superconductors under intense photoexcitation.

Findings

Inelastic scattering decreases below the critical temperature.

Robust pairing amplitude persists beyond the superconducting phase.

No direct link between pairing amplitude and pseudogap observed.

Abstract

We perform time resolved photoelectron spectroscopy measurements of optimally doped $\tn{Bi}_2\tn{Sr}_2\tn{CaCu}_2\tn{O}_{8+\delta}$ (Bi-2212) and $\tn{Bi}_2\tn{Sr}_{2-x}\tn{La}_{x}\tn{Cu}\tn{O}_{6+\delta}$ (Bi-2201). The electrons dynamics show that inelastic scattering by nodal quasiparticles decreases when the temperature is lowered below the critical value of the superconducting phase transition. This drop of electronic dissipation is astonishingly robust and survives to photoexcitation densities much larger than the value sustained by long-range superconductivity. The unconventional behaviour of quasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to the inelastic path. Our measurements indicate that strongly driven superconductors enter in a regime without phase coherence but finite pairing amplitude. The latter vanishes near to the critical temperature and has no evident link with the pseudogap observed by Angle Resolved Photoelectron Spectroscopy (ARPES).