Abnormalities of the thermal expansion of Bi2Sr2-x La x CuO6 + δ high-temperature superconductor in the dielectric phase (x ≥ 0.8) and charge ordering in an oxygen sublattice

Abstract

Abnormal negative thermal expansion of single crystals of high-temperature Bi2Sr2 − xLaxCuO6 + · superconductor in the dielectric phase (x ≥ 0.8) was detected at low temperatures. It was established that material shrinkage upon heating occurs at higher temperatures than in superconducting compositions. The anisotropic and nonmonotonous effect of a magnetic field of 3–6 T on the coefficient of thermal expansion was revealed. We attribute these abnormalities to the existence of superstructure charge ordering in the oxygen sublattice.