Collapse of superconductivity in cuprates via ultrafast quenching of phase coherence

TL;DR

This study demonstrates that ultrafast light pulses can rapidly disrupt phase coherence in cuprate superconductors, causing a transition to the normal state without affecting pairing strength, revealing the critical role of phase coherence.

Contribution

It provides direct experimental evidence of phase coherence collapse as the mechanism for superconductivity loss in cuprates using ultrafast spectroscopy.

Findings

Ultrafast pulses melt superconductivity without weakening pairing

Phase fluctuations dominate the superconductor-to-normal transition

Time-resolved spectroscopy disentangles charge and phase dynamics

Abstract

The possibility of driving phase transitions in low-density condensates through the loss of phase coherence alone has far-reaching implications for the study of quantum phases of matter. This has inspired the development of tools to control and explore the collective properties of condensate phases via phase fluctuations. Electrically-gated oxide interfaces, ultracold Fermi atoms, and cuprate superconductors, which are characterized by an intrinsically small phase-stiffness, are paradigmatic examples where these tools are having a dramatic impact. Here we use light pulses shorter than the internal thermalization time to drive and probe the phase fragility of the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ cuprate superconductor, completely melting the superconducting condensate without affecting the pairing strength. The resulting ultrafast dynamics of phase fluctuations and charge excitations are captured and disentangled by time-resolved photoemission spectroscopy. This work demonstrates the dominant role of phase coherence in the superconductor-to-normal state phase transition and offers a benchmark for non-equilibrium spectroscopic investigations of the cuprate phase diagram.