• Hänisch, J.
• Iida, K.
• Kurth, F.
• Teresiak, A.
• Skrotzki, W.
• Ahrens, E.
• Grinenko, Vadim
• Aswartham, S.
• Mönch, I.
• Ichinose, A.
• Wurmehl, S.
• Efremov, D. V.
• Pukenas, A.
• Holzapfel, B.
• Drechsler, S. L.
• Hühne, R.
• Erbe, M.
• Tsukada, I.
• Chekhonin, P.

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 , 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(Fe₁₋ₓCoₓ)₂As₂ 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 BaFe₂As₂ system.

Topics

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