Dependence of NQR frequency, ν Q(Cu) on pressure up to 1.3GPa is reported for La1.85Sr0.15CuO4 and YBa2Cu4O8. Correlations are found between some physical quantities and the ratio of the hole density in Cu2 to that in 02(3), n(Cu2)/n(O2,3) which is extracted from ν Q's. It is proposed that there exists an optimum of n(Cu2)/n(O2,3) for Tc and that the increase of Tc under pressure is due to the approach of n(Cu2)/n(O2,3) to the optimum through the local hole transfer.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering