Effect of external magnetic field on superconducting and spin density wave gaps of high-Tc superconductors

A theoretical model is addressed here to study the interplay of the superconductivity (SC) and the spin density wave (SDW) long range orders in underdoped region in the vicinity of on-set of superconductivity in presence of an external magnetic field. The order parameters are calculated by using Zubarev's technique of Green's functions and determined numerically self-consistently. The gap parameters are found to be strongly coupled to each other through their coupling constants. The interplay displays BCS type two gaps in the quasi-particle density of states (DOS) which resemble the tunneling conductance of STM experiments. The gap edges in the DOS appear at +/-(z + z(1)) and +/-(z - z(1)). The applied magnetic field on the basis of spin-filter effect of tunneling further induces Zeeman splitting which is explained experiment. (c) 2009 Elsevier B.V. All rights reserved.