Abrupt recovery of Fermi-liquid transport following the collapse of the c axis in CaFe₂(As_1-xP_x)₂ single crystals

Single crystals of CaFe₂(As_1-xP_x) ₂ are found to exhibit the tetragonal (T) to collapsed-tetragonal (cT) transition at T_cT100 K for x0.05. The c-axis shrinks by ~9% below T_cT, which substantially diminishes the interband nesting between the hole and electron bands. In sharp contrast to the superconducting T phase of AFe₂(As_1-xP_x)₂ (A= Ba, Sr), where the anomalous non-Fermi liquid transport properties are observed, the resistivity, Hall coefficient, and magnetoresistance data in the Ca-based system all indicate that the standard Fermi liquid behaviors are recovered abruptly below T_cT, and the superconductivity disappears completely. The simultaneous disappearance of the superconductivity and the non-Fermi liquid transport enlightens the essential role of interband-associated fluctuations to the superconductivity in Fe pnictides.