Thermoelectric power and irreversibility field of (Hg,Tl) 2Ba 2Ca n−1 Cu nO y ( n=2–5) superconductors

Abstract

We have measured the thermoelectric power, S, and the irreversibility field, H irr, of the superconducting samples of (Hg,Tl) 2Ba 2Ca n−1 Cu n O y ( n=2–5). S values for the (Hg,Tl)-22( n−1) n above their T c's drastically increase with increasing n. Judging from the S values at room temperature, the n=2 and 3 samples are located in the overdoped region, the n=4 is in the almost optimally doped and the n=5 is in the underdoped region. H irr values for the n=4 and 5 samples are higher than those for the as-synthesized and annealed n=3 samples. It is considered that the enhancement in H irr is due not only to the increase of hole concentration but to the increase in the number of CuO 2 sheets.