2D XY Ordering in Striped Cu-O Planes in Underdoped Bi-2212
  It was discussed the possibility of determination of 2D XY ordering temperature (Berezinskii-Kosterlitz-Thouless temperature) in striped Cu-O planes for quasi-two dimensional HTS with the semiconducting behavior of out-of-plane resistivity in normal state. From the results of the resistivity measurements for samples of underdoped Bi-2212 the values of 2D XY ordering temperature were found out. Its are compared with the results of the measurements of frequency dependent conductivity. It is shown that these both results give the value of 2D XY ordering temperature ~62 K for samples with Tc=74 K and verify the importance of taken into account two dimensional superconducting fluctuations at T>Tc. 
G.G.Sergeeva