High-pressure spin shifts in the pseudogap regime of superconducting YBa2Cu4O8 as revealed by 17O NMR

A NMR anvil cell design is used for measuring the influence of high pressure on the electronic properties of the high-temperature superconductor YBa2Cu4O8 above the superconducting transition temperature T-c. It is found that pressure increases the spin shift at all temperatures in such a way that the pseudogap feature has almost disappeared at 63 kbar. This change of the temperature-dependent spin susceptibility can be explained by a pressure-induced proportional decrease (factor of 2) of a temperature-dependent component, and an increase (factor of 9) of a temperature-independent component, contrary to the effects of increasing doping. The results demonstrate that one can use anvil cell NMR to investigate the tuning of the electronic properties of correlated electronic materials with pressure.