Large temperature dependence of the number of carriers in Co-doped BaFe2As2

TL;DR

This study investigates how the number of charge carriers in Co-doped BaFe2As2 varies significantly with temperature, revealing a strong temperature dependence linked to band shifts and fluctuations, which impacts the material's electronic properties.

Contribution

The paper demonstrates a large temperature-dependent change in carrier number in Ba(Fe,Co)2As2, highlighting the role of k-dependent band shifts and fluctuations, which were not previously characterized.

Findings

Carrier number varies up to 50% with temperature.

k-dependent energy shifts are significant at low Co content.

Temperature influences band shifts and carrier populations.

Abstract

Using angle-resolved photoemission spectroscopy, we study the evolution of the number of carriers in Ba(Fe(1-x)Cox)2As2 as a function of Co content and temperature. We show that there is a k-dependent energy shift compared to density functional calculations, which is large at low Co contents and low temperatures and reduces the volume of hole and electron pockets by a factor 2. This k-shift becomes negligible at high Co content and could be due to interband charge or spin fluctuations. We further reveal that the bands shift with temperature, changing significantly the number of carriers they contain (up to 50%). We explain this evolution by thermal excitations of carriers among the narrow bands, possibly combined with a temperature evolution of the k-dependent fluctuations.