Shadow bands in overdoped Bi_2Sr_2CaCu_2O_{8+x}

TL;DR

This study uses angle-resolved photoemission to identify a shadow peak in overdoped Bi-2212, suggesting it arises from spin fluctuations rather than structural effects, with implications for understanding high-temperature superconductivity.

Contribution

It provides evidence that the shadow peak in overdoped Bi-2212 is due to spin fluctuations, not structural artifacts, advancing understanding of spectral features in cuprates.

Findings

Shadow peak shifts by (π,π) from quasiparticle peak

Shadow/quasiparticle amplitude ratio increases with binding energy

Shadow peak linked to spin fluctuations at (π,π)

Abstract

We performed angle-resolved photoemission experiments on overdoped single crystal $Bi_2Sr_2CaCu_2O_{8+x}$ samples with Tc values as low as 55K and very narrow transitions as measured by AC susceptibility. The photoemission data indicate the presence of a ``shadow'' peak in the quasiparticle spectral function $A(\omega)$ shifted by $(\pi,\pi)$ from the conventional quasiparticle peak. The ratio of the shadow/quasiparticle peak amplitudes strongly increases with the binding energy. This is consistent with the idea that the shadow peak is not a structural replica of the quasiparticle peak, but rather a maximum in a spectral function which can exist due to interaction with spin fluctuations peaked at $(\pi,\pi)$.