Abnormal electronic transport properties with Hall effect, magneto-resistivity, and phase diagram in CaFeAsF single crystals

Abstract

An iron-based superconductor 1111-system exhibits rich physical properties, which can provide a very good material platform for the study of superconducting properties. Recently, it has been found that annealed CaFeAsF single crystals may lead to the valence reconfiguration of polyvalent Fe, which introduces superconductivity in CaFeAsF single crystals. Those results make research on CaFeAsF single crystals one of the hot topics in the study of superconductivity. However, many fundamental physical properties of parent CaFeAsF have not yet been systematically studied, especially the abnormal transitions in its temperature-dependent transport behavior. Here, transport measurements have been systematically investigated on CaFeAsF single crystals. The multi-band nature was verified by Hall conductivity. Meanwhile, above ∼40 K, the hole carrier concentration disappeared according to Hall conductivity analysis. In order to clarify the intrinsic origin of abnormal electronic transport behavior, we carefully check the magneto-resistivity, angular magneto-resistivity, and specific heat behavior. Combining those results and discussion, we speculate that this abnormal electronic transport behavior has a close relationship with the changed Fermi surface. Finally, we constructed a complete B-T phase diagram of CaFeAsF, which can provide some physical foundations for further study of the superconducting properties in the 1111-system.