Abrupt recovery of Fermi-liquid transport by the c-axis collapse in CaFe2(As1-xPx)2 single crystals

TL;DR

This study shows that in CaFe$_2$(As$_{1-x}$P$_x$)$_2$ single crystals, a transition to a collapsed-tetragonal phase causes an abrupt recovery of Fermi-liquid transport properties and the disappearance of superconductivity, highlighting the role of interband fluctuations.

Contribution

It reveals that the c-axis collapse in CaFe$_2$(As$_{1-x}$P$_x$)$_2$ induces a sudden shift from non-Fermi liquid to Fermi-liquid behavior, contrasting with other Fe-based superconductors.

Findings

c-axis shrinks by ~9% below T_cT

Fermi-liquid behavior recovers abruptly below T_cT

Superconductivity disappears after the transition

Abstract

Single crystals of CaFe$_2$(As$_{1-x}$P$_x$)$_2$ are found to exhibit the tetragonal (T) to collapsed-tetragonal (cT) transition at $T_{\rm cT} \lesssim100$\,K for $x>0.05$. The c-axis shrinks by $\sim9$% below $T_{\rm cT}$, which substantially diminishes the interband nesting between the hole and electron bands. In sharp contrast to the superconducting T phase of $A$Fe$_2$(As$_{1-x}$P$_x$)$_2$ ($A=$ 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 $T_{\rm cT}$, and the superconductivity disappears completely. The intimate link between the superconductivity and the non-Fermi liquid transport enlightens the essential role of interband-associated fluctuation effects in Fe-pnictides.