ELECTRONIC STRUCTURE OF Hg0.8Pb0.2Ba2Ca2Cu3O8+δ: THE ROLE OF Pb DOPING, OXYGEN DOPING AND HIGH PRESSURE

The effects of Pb doping, oxygen doping (δ= 0.1,0.2,0.4 and 0.5) and high pressate (4, 8, 15 and 20GPa) on the electronic structure of Hg0.8Pb0.2Ba2Ca2Cu3O8+δ have been examined by the recursion method. Our calculations show that Pb doping only decreases the hole concentration slightly and oxygen doping increases the hole concentration monotonically and significantly as δ varies from 0 to 0.5, with each excess oxygen atom contributing about 1.7 holes to the CuO2 layers. The optimal δ is estimated to be around 0.4, The hole conceatration increases initially with pres-sure but decreases as P > 8GPa (i.e., dn/dP does change sign at ～ 8GPa). The suppressed Tc(P) by Pb substitution has to be described in the modified Neumeier's model.