Effect of Oxygen Redistribution on Temperature Dependence of Pseudo-Gap in Underdoped $HoBa_{2}Cu_{3}O_{7-δ}$ Single Crystals

The effect of annealing at room temperature on the excess conductivity of oxygen deficient $HoBa_2Cu_{3}O_{7 - δ}$ single crystal is studied. It is shown that there is substantial extension of the interval of linear dependence $ρ_{ab}$ (T) and narrowing of the temperature area of the pseudo-gap regime as a result of annealing. The excess conductivity satisfies the exponential temperature dependence in a wide temperature interval. The temperature dependence of the pseudogap is satisfactorily described by the BCS-BEC theoretical model.