Melting of Charge Stripes in Vibrationally Driven La1.875Ba0.125CuO4: Assessing the Respective Roles of Electronic and Lattice Order in Frustrated Superconductors

TL;DR

This study uses femtosecond X-ray diffraction to investigate how charge order and lattice structure in La1.875Ba0.125CuO4 respond to vibrational excitation, revealing that charge stripes melt rapidly while lattice distortions change slowly, impacting superconductivity understanding.

Contribution

It provides direct time-resolved measurements showing charge order melts faster than lattice distortions, clarifying their roles in superconductivity suppression.

Findings

Charge stripe order melts within sub-picoseconds.

Lattice distortions respond on longer timescales.

Charge modulations, not lattice distortions, inhibit superconductivity.

Abstract

We report femtosecond resonant soft X-ray diffraction measurements of the dynamics of the charge order and of the crystal lattice in non-superconducting, stripe-ordered La1.875Ba0.125CuO4. Excitation of the in-plane Cu-O stretching phonon with a mid-infrared pulse has been previously shown to induce a transient superconducting state in the closely related compound La1.675Eu0.2Sr0.125CuO4. In La1.875Ba0.125CuO4, we find that the charge stripe order melts promptly on a sub-picosecond time scale. Surprisingly, the low temperature tetragonal distortion is only weakly reduced, reacting on significantly longer time scales that do not correlate with light-induced superconductivity. This experiment suggests that charge modulations alone, and not the LTT distortion, prevent superconductivity in equilibrium.