Competition between the Pseudogap and Superconducting States of Bi$_{2}$Sr$_{2}$Ca$_{0.92}$Y$_{0.08}$Cu$_{2}$O$_{8+\delta}$ Single Crystals Revealed by Ultrafast Broadband Optical Reflectivity

TL;DR

This study uses ultrafast broadband optical reflectivity to investigate the dynamic competition and coexistence of pseudogap and superconducting states in a cuprate crystal, revealing weak phase competition.

Contribution

It provides new insights into the interplay between pseudogap and superconductivity through time-resolved optical measurements and coupled differential equations modeling.

Findings

Pseudogap relaxation accelerates in the superconducting state.

Transient reflectivity changes sign after ~0.5 ps.

Weak coupling indicates coexistence of phases.

Abstract

Ultrafast broadband transient reflectivity experiments are performed to study the interplay between the non-equilibrium dynamics of the pseudogap and the superconducting phases in Bi$_{2}$Sr$_{2}$Ca$_{0.92}$Y$_{0.08}$Cu$_{2}$O$_{8+\delta}$. Once superconductivity is established the relaxation of the pseudogap proceeds $\sim$ 2 times faster than in the normal state, and the corresponding transient reflectivity variation changes sign after $\sim$ 0.5 ps. The results can be described by a set of coupled differential equations for the pseudogap and for the superconducting order parameter. The sign and strength of the coupling term suggest a remarkably weak competition between the two phases, allowing their coexistence.