Nernst effect in oxygen-depleted SmBa 2Cu 3O 6+ x single crystals

Abstract

The transport properties and Nernst effect of underdoped SmBa 2Cu 3O 6+ x single crystals were measured. As hole concentration p decreases from 0.142 to 0.096, T c0 decreases monotonously from 90 K to 60 K, and the pseudogap opening temperature ( T ∗) increases from 163 K to 233 K. The onset temperature ( T v) of vortex-like excitation detected by Nernst effect decreases with decreasing p as T c0 does. The results suggest that the pseudogap state is divided into two different regimes by the characteristic temperature T v. The regime between T c and T v is dominated by strong phase fluctuations. This temperature regime ( T c0 < T < T v) is much narrower compared to the underdoped La 2− x Sr x CuO 4.