NMR observation of charge fluctuations in quasi-one-dimensional cuprates Original Research Article

Results of the Cu NMR/NQR experiments are presented for the nearly quarter-filled zigzag chain compound PrBa2Cu4O8 and the hole-doped two-leg ladder material Sr14−xCaxCu24O41. A pronounced peak is found in the temperature dependence of the nuclear spin–lattice and the nuclear spin–spin relaxation rates in PrBa2Cu4O8. The ratio of these rates for 63Cu and 65Cu indicates that the relaxation at the peak is caused by fluctuations of electric field gradient. Similar behavior was observed in Sr14−xCaxCu24O41 for x>3. We propose that gradual slowing down of electronic charge fluctuations and partial charge freezing occur in these materials.