Single crystal growth and physical property study of 1111-type Fe-based superconducting system CaFeAsF

Since Fe-based high temperature superconductor was discovered in 2008, its material exploration and physical properties have been widely and in depth studied. However, the 1111 system, which was discovered first to have the highest T-c in the bulk material, has long been lacking in large-size and high-quality single-crystalline sample. This seriously restricts the in-depth study of the physical problems relating to this material system. In recent years, the great progress of single crystal growth of the fluorine-based 1111 system CaFeAsF has been made. One has successfully grown the high-quality CaFeAsF parent phase and Co doped superconducting single crystal with millimeter size at ambient pressure by using CaAs as the flux. On this basis, several research groups have studied the physical properties of this system by different experimental means and obtained some important results. For example, Dirac Fermions have been detected in CaFeAsF single crystal by measuring the quantum oscillation and optical conductivity. A high-field-induced metal-insulator transition was reported in CaFeAsF, which is closely related to the quantum limit. This review is intended to make a preliminary summary of the progress of this area, including crystal growth, quantum oscillation, infrared spectrum, magnetoresistance under strong field, high pressure regulation, anisotropy, superconducting fluctuations, etc.