Electron-phonon anomaly related to charge stripes: static stripe phase versus optimally-doped superconducting La1.85Sr0.15CuO4

TL;DR

This study reveals a universal phonon anomaly linked to charge stripes in cuprates, observed in both static stripe-ordered and optimally doped superconducting phases, indicating stripe-related phenomena are more widespread than previously thought.

Contribution

It demonstrates that phonon anomalies associated with charge stripes occur in optimally doped La1.85Sr0.15CuO4, extending the understanding of stripe phenomena beyond the 1/8 anomaly region.

Findings

Phonon anomalies are similar across different cuprates with stripe order.

The anomaly persists in optimally doped superconductors, indicating dynamic stripes.

Conventional band theory does not predict these phonon anomalies.

Abstract

Inelastic neutron scattering was used to study the Cu-O bond-stretching vibrations in optimally doped La1.85Sr0.15CuO4 (Tc = 35 K) and in two other cuprates showing static stripe order at low temperatures, i.e. La1.48Nd0.4Sr0.12CuO4 and La1.875Ba0.125CuO4. All three compounds exhibit a very similar phonon anomaly, which is not predicted by conventional band theory. It is argued that the phonon anomaly reflects a coupling to charge inhomogeneities in the form of stripes, which remain dynamic in superconducting La1.85Sr0.15CuO4 down to the lowest temperatures. These results show that the phonon effect indicating stripe formation is not restricted to a narrow region of the phase diagram around the so-called 1/8 anomaly but occurs in optimally doped samples as well.