SUPERCONDUCTIVITY AND HOLE SOURCE IN HG(BA2-XSRX)CUO4+DELTA

Mercury cuprates Hg(Ba2-xSrx)CuO4+delta (x = 0.0-0.7) were synthesized , and their structure and superconductivity were characterized. Single phases of Hg(Ba2-xSrx)CuO4+delta can be obtained for x = 0.0-0.7; the y crystallize in a tetragonal structure, and their a- and c-parameters decrease smoothly with increasing x. The superconducting transition t emperature of Hg(Ba2-xSrx)CuO4+delta decreases with increasing x, and superconductivity vanishes for x greater-than-or-equal-to 0.5. These o bservations and tight-binding electronic band structure calculations s uggest that the hole source of Hg(Ba2-xSrx) CuO4+delta is not the Hg 6 s band but the interstitial oxygen atoms in the HgO(delta) sheet. (C) 1994 Academic Press, Inc.