Pseudogap-like phase in Ca(Fe$_{1-x}$Co$_x$)$_2$As$_2$ revealed by   $^{75}$As NQR
  We report $^{75}$As NQR measurements on single crystalline Ca(Fe$_{1-x}$Co$_x$)$_2$As$_2$ ($0\leq x \leq 0.09$). The nuclear spin-lattice relaxation rate $T_1^{-1}$ as a function of temperature $T$ and Co dopant concentration $x$ reveals a normal-state pseudogap-like phase below a crossover temperature $T^*$ in the under- and optimally-doped region. The resulting $x$-$T$ phase diagram shows that, after suppression of the spin-density-wave order, $T^*$ intersects $T_c$ falling to zero rapidly near the optimal doping regime. Possible origins of the pseudogap behavior are discussed. 
S.-H. Baek, H.-J. Grafe, L. Harnagea, S. Singh, S. Wurmehl, and B.   B\"uchner
cond-mat.supr-con