• Ichinose, Ataru
• Wurmehl, Sabine
• Moench, Ingolf
• Huehne, Ruben
• Erbe, Manuela
• Haenisch, Jens
• Grinenko, Vadim
• Drechsler, Stefan-Ludwig
• Holzapfel, Bernhard
• Iida, Kazumasa
• Tsukada, Ichiro
• Teresiak, Angelika
• Efremov, Dmitri V.
• Skrotzki, Werner
• Aswartham, Saicharan
• Kurth, Fritz
• Pukenas, Aurimas
• Chekhonin, Paul
• Ahrens, Eike

Abstract

The Hall effect is a powerful tool for investigating carrier type and density. For single-band materials, the Hall coefficient is traditionally expressed simply by $R_H^{-1} = -en$, where $e$ is the charge of the carrier, and $n$ is the concentration. However, it is well known that in the critical region near a quantum phase transition, as it was demonstrated for cuprates and heavy fermions, the Hall coefficient exhibits strong temperature and doping dependencies, which can not be described by such a simple expression, and the interpretation of the Hall coefficient for Fe-based superconductors is also problematic. Here, we investigate thin films of Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ with compressive and tensile in-plane strain in a wide range of Co doping. Such in-plane strain changes the band structure of the compounds, resulting in various shifts of the whole phase diagram as a function of Co doping. We show that the resultant phase diagrams for different strain states can be mapped onto a single phase diagram with the Hall number. This universal plot is attributed to the critical fluctuations in multiband systems near the antiferromagnetic transition, which may suggest a direct link between magnetic and superconducting properties in the BaFe$_2$As$_2$ system. ; Comment: Accepted for publication in Scientific Reports, 6 main figures plus Supplemental Information (8 figures)

Topics

• density
• impedance spectroscopy
• compound
• phase
• thin film
• phase transition
• phase diagram
• band structure