Observation of hexatic liquid vortex matter in YBa2Cu3O7

TL;DR

This study uses an atomic beam probe to observe a hexatic vortex liquid phase in YBa2Cu3O7, revealing a state with orientational order but short-range positional correlation near the superconducting transition.

Contribution

First direct observation of a hexatic vortex liquid phase in a high-temperature superconductor using atomic beam probing.

Findings

Vortex configuration exhibits bond-orientational order with short-range translational correlation.

Hexatic vortex liquid exists in thermal equilibrium just below T_C.

At low temperatures, the vortex state becomes a quenched hexatic glass.

Abstract

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.