Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 36: SC: Fe-based Superconductors - 122 - Properties, Electronic Structure, Mechanisms

TT 36.16: Talk

Wednesday, March 16, 2011, 18:15–18:30, HSZ 304

Pseudogap-like phase in Ca(Fe_1−xCo_x)₂As₂ revealed by ⁷⁵As NQR — •Seung-Ho Baek, Hans-Joachim Grafe, Guillaume Lang, Lumanita Harnagea, S. Singh, Sabine Wurmehl, and Bernd Buechner — IFW-Dresden, Institute for Solid State Research, PF 270116, 01171 Dresden, Germany

We report ⁷⁵As nuclear quadrupole resonance (NQR) measurements on single crystalline Ca(Fe_1−xCo_x)₂As₂ (0 < x < 0.09). The nuclear spin-lattice relaxation rate T₁⁻¹ 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 are discussed.