Abstract
Nuclear quadrupole interactions and charge localization in HgBa2CuO4+d with different oxygen content
Variation of the oxygen content d in
HgBa2CuO4+d (Hg-1201) provides
a good opportunity to study the influence of oxygen doping on nuclear quadrupole
interactions (NQI) and charge localisation in different regions of the
(Tc-d) phase diagram. We performed
63,65Cu Nuclear Quadrupole Resonance (NQR) studies on a series
of HgBa2CuO4+d samples with
different oxygen content d. Based on the experimental
NQR spectra of the Hg-1201 compounds and the known copper NQR frequency for
the undoped Nd2CuO4 a phenomenological method is developed
to analyze the NQI in high temperature superconductors (HTSC) including both,
the on-site electric field gradient (EFG) and the lattice contribution in
the EFG. Using this method we estimated the Sternheimer antishielding factor
g¥ = - 16.2 for Cu2+
and the hole concentration nx2-y2 on the copper 3dx2-y2
orbital. The nx2-y2 value rises monotonously with increasing doping
level over the whole Hg-1201 sample series and is the main factor causing
the increase of quadrupole frequency
n0 . No saturation effect on the copper
hole doping process has been found at high oxygen content level.