The evolution of Fermi surface (FS) states of ${\mathrm{NdFeAs}}_{1-x}{\mathrm{P}}_x{\mathrm{O}}_{0.9}{\mathrm{F}}_{0.1}$ single crystals with As/P substitution has been investigated. The critical temperature $T_c$ and the power-law exponent ($n$) of temperature-dependent resistivity $[\rho \left(T\right)={\rho }_0+A{T}^n]$ show a clear correlation above $x=0.2$, suggesting that $T_c$ is enhanced with increasing bosonic fluctuations in the same type of FS state. Around $x=0.2$, all the transport properties show anomalies, indicating that $x\sim 0.2$ is the critical composition of a drastic FS change. Angle-resolved photoemission spectroscopy has more directly revealed the distinct change of FS around $x=0.2$, that one hole FS disappears at the Brillouin zone center and the other FS with a propellerlike shape appears at the zone corner with decreasing $x$. These results are indicative of the existence of two types of FS states with different nesting conditions that are related with two $T_c$-raising mechanisms in this system.

• Received 17 May 2018
• Revised 10 August 2018

DOI:https://doi.org/10.1103/PhysRevB.98.100501