Crossover near the fluctuation-induced first-order transition in superconductors is studied to first order in $\epsilon =4-d$. We find that the effective exponent ${\gamma }_{\mathrm{eff}}$ for the susceptibility of type-II systems falls from its value for the chargeless system to the mean-field value unity well before the first-order transition occurs. Although such effects are probably unobservable in real superconductors, these calculations may have some relevance to the nematic to smectic-$A$ transition in liquid crystals.

• Received 9 January 1978

DOI:https://doi.org/10.1103/PhysRevB.17.4274