THEORY OF A CONTINUOUS H-C2 NORMAL-TO-SUPERCONDUCTING TRANSITION

I study the Hc2 transition within the Ginzburg-Landau model, with m-component order parameter ψi. I find a renormalized fixed point free energy, exact in m→limit, suggestive of a second-order transition in contrast to the general belief of a first-order transition. The thermal fluctuations for H0 force one to consider an infinite set of marginally relevant operators for d<duc=6. I find dlc=4, predicting that the off-diagonal long-range order does not survive thermal fluctuations in d=2,3. The result is a solution to a critical fixed point that was found to be inaccessible within ε=6-d expansion, previously considered by Brezin, Nelson, and Thiaville [Phys. Rev. B 31, 7124 (1985)], and was interpreted as a first-order transition. © 1995 The American Physical Society.