Effect of fluctuations on vortex lattice structural transitions in superconductors

الأصل · EN

The rhombic-to-square transition field H(T) for cubic and tetragonal materials in fields along [001] is evaluated using the nonlocal London theory with account of thermal vortex fluctuations. Unlike extended Ginzburg-Landau models, our approach shows that the line H(T) and the upper critical field Hc₂(T) do not cross due to strong fluctuations near Hc₂(T) which suppress the square anisotropy induced by the nonlocality. In increasing fields, this causes re-entrance of the rhombic structure in agreement with recent neutron scattering data on borocarbides.