Photo-enhanced metastable c-axis electrodynamics in stripe ordered cuprate La$_{1.885}$Ba$_{0.115}$CuO$_{4}$

TL;DR

This study demonstrates that near-infrared light pulses can induce a metastable state in stripe-ordered cuprate La$_{1.885}$Ba$_{0.115}$CuO$_{4}$, significantly enhancing its superconducting fluctuations and altering charge order dynamics.

Contribution

It provides direct evidence that optical excitation can modify the balance of competing orders in cuprates, leading to a metastable state with enhanced superconducting properties.

Findings

Photo-excitation increases far-infrared spectral weight by over an order of magnitude.

Blueshift of the Josephson Plasma Resonance indicates non-thermal charge order collapse.

Metastable state persists beyond 300 ps with signs of spatial inhomogeneity.

Abstract

Quantum materials are amenable to non-equilibrium manipulation with light, enabling modification and control of macroscopic properties. Light-based augmentation of superconductivity is particularly intriguing. Copper-oxide superconductors exhibit complex interplay between spin order, charge order and superconductivity, offering the prospect of enhanced coherence by altering the balance between competing orders. We utilize terahertz time domain spectroscopy to monitor the c-axis Josephson Plasma Resonance (JPR) in La$_{2-x}$Ba$_{x}$CuO$_{4}$ (x = 0.115) as a direct probe of superconductivity dynamics following excitation with near infrared pulses. Starting from the superconducting state, c-axis polarized excitation with a fluence of 100 $\mu$J/cm2 results in an increase of the far-infrared spectral weight by more than an order of magnitude as evidenced by a blueshift of the JPR, interpreted as resulting from non-thermal collapse of the charge order. The photo-induced signal persists well beyond our measurement window of 300 ps and exhibits signatures of spatial inhomogeneity. The electrodynamic response of this new metastable state is consistent with enhanced superconducting fluctuations. Our results reveal that La$_{2-x}$Ba$_{x}$CuO$_{4}$ is highly sensitive to non-equilibrium excitation over a wide fluence range, providing an unambiguous example of photo-induced modification of order-parameter competition.