Doping Dependence of Spin Dynamics in Electron-Doped Ba(Fe1-xCox)2As2

TL;DR

This study investigates how electron doping affects spin dynamics in Ba(Fe1-xCox)2As2 using inelastic neutron scattering, revealing changes in magnetic fluctuations and excitations across different doping levels.

Contribution

It provides a comprehensive analysis of spin dynamics across the full doping range, highlighting the evolution of magnetic excitations and their relation to superconductivity and Fermi surface topology.

Findings

Damped magnetic fluctuations in optimally doped compound similar to parent compound

Magnetic excitations in overdoped superconductor show a gap-like behavior

Magnetic scattering disappears in heavily overdoped, non-superconducting sample

Abstract

The spin dynamics in single crystal, electron-doped Ba(Fe1-xCox)2As2 has been investigated by inelastic neutron scattering over the full range from undoped to the overdoped regime. We observe damped magnetic fluctuations in the normal state of the optimally doped compound (x=0.06) that share a remarkable similarity with those in the paramagnetic state of the parent compound (x=0). In the overdoped superconducting compound (x=0.14), magnetic excitations show a gap-like behavior, possibly related to a topological change in the hole Fermi surface (Lifshitz transition), while the imaginary part of the spin susceptibility prominently resembles that of the overdoped cuprates. For the heavily overdoped, non-superconducting compound (x=0.24) the magnetic scattering disappears, which could be attributed to the absence of a hole Fermi-surface pocket observed by photoemission.