Doping dependence of the $(\pi,\pi)$ shadow band in La-based cuprates studied by angle-resolved photoemission spectroscopy

TL;DR

This study investigates the doping dependence of the $(,)$ shadow band in La-based cuprates using ARPES, revealing a strong doping-dependent intensity over a wide doping range, with implications for understanding cuprate electronic structure.

Contribution

It provides the first comprehensive doping-dependent analysis of the shadow band in La214 cuprates, challenging previous notions of its doping range and linking it to lattice distortions.

Findings

Shadow band intensity is strongest at low doping (~0.03) and diminishes with doping.

The shadow band exists over a wide doping range, not just near 1/8.

Lattice distortion is a more plausible origin than antiferromagnetic fluctuations.

Abstract

The $(\pi,\pi)$ shadow band (SB) in La-based cuprate family (La214) was studied by angle-resolved photoemission spectroscopy (ARPES) over a wide doping range from $x=0.01$ to $x=0.25$. Unlike the well-studied case of the Bi-based cuprate family, an overall strong, monotonic doping dependence of the SB intensity at the Fermi level ($E_F$) was observed. In contrast to a previous report for the presence of the SB only close to $x=1/8$, we found it exists in a wide doping range, associated with a doping-independent $(\pi,\pi)$ wave vector but strongly doping-dependent intensity: It is the strongest at $x\sim 0.03$ and systematically diminishes as the doping increases until it becomes negligible in the overdoped regime. This SB with the observed doping dependence of intensity can in principle be caused by the antiferromagnetic fluctuations or a particular form of low-temperature orthorhombic lattice distortion known to persist up to $x\sim 0.21$ in the system, with both being weakened with increasing doping. However, a detailed binding energy dependent analysis of the SB at $x=0.07$ does not appear to support the former interpretation, leaving the latter as a more plausible candidate, despite a challenge in quantitatively linking the doping dependences of the SB intensity and the magnitude of the lattice distortion. Our finding highlights the necessity of a careful and global consideration of the inherent structural complications for correctly understanding the cuprate Fermiology and its microscopic implication.