Ultrafast Dynamics of Bilayer and Trilayer Nickelate Superconductors

TL;DR

This study uses ultrafast reflectivity to compare the dynamics of bilayer and trilayer nickelate superconductors, revealing distinct behaviors related to density-wave transitions and electron-phonon interactions at ambient pressure.

Contribution

It provides the first ultrafast dynamics comparison of bilayer and trilayer nickelates, highlighting differences in phonon modes and transition behaviors, and estimates electron-phonon coupling constants.

Findings

Presence of a coherent phonon mode in La4Ni3O10

Divergent relaxation times near density-wave transition in La4Ni3O10

Electron-phonon coupling is minor in both compounds

Abstract

In addition to the pressurized high-temperature superconductivity, bilayer and trilayer nickelate superconductors Lan+1NinO3n+1 (n = 2 and 3) exhibit many intriguing properties at ambient pressure, such as orbital-dependent electronic correlation, non-Fermi liquid behavior, and density-wave transitions. Here, using ultrafast reflectivity measurement, we observe a drastic difference between the ultrafast dynamics of the bilayer and trilayer nickelates at ambient pressure. Firstly, we observe a coherent phonon mode in La4Ni3O10 involving the collective vibration of La, Ni, and O atoms, which is absent in La3Ni2O7. Secondly, the temperature-dependent relaxation time diverges near the density-wave transition temperature of La4Ni3O10, in drastic contrast to kink-like changes in La3Ni2O7. Moreover, we estimate the electron-phonon coupling constants to be 0.05~0.07 and 0.12~0.16 for La3Ni2O7 and La4Ni3O10, respectively, suggesting a relatively minor role of electron-phonon coupling in the electronic properties of Lan+1NinO3n+1. Our work not only sheds light on the relevant microscopic interaction but also establishes a foundation for further studying the interplay between superconductivity and density-wave transitions in nickelate superconductors.