An atomic beam probe is used to study the structure and dynamics of quantized supercurrent vortex lines in YBa_{2}Cu_{3}O_{7-?} at temperatures up to within 0.7 K below T_{C}. Here we report the direct observation of a vortex configuration with sample wide bond-orientational order but only short range translational correlation. The data imply the existence of an intermediate `hexatic' vortex line liquid phase. We find that the hexatic liquid is in thermal equilibrium over a narrow temperature range below T_{C} and is quenched into an immobile hexatic glass at low temperatures.
@article{arxiv.cond-mat/0209632,
title = {Observation of hexatic liquid vortex matter in YBa2Cu3O7},
author = {Harald Hauglin and Nathan G. Woodard and Gregory P. Lafyatis},
journal= {arXiv preprint arXiv:cond-mat/0209632},
year = {2007}
}