Coulomb Gap and Correlated Vortex Pinning in Superconductors

The positions of columnar pins and magnetic flux lines determined from a decoration experiment on BSCCO were used to calculate the single–particle density of states at low temperatures in the Bose glass phase. A wide Coulomb gap is found, with gap exponent s ≈ 1 .2, as a result of the long–range interaction between the vortices. As a consequence, the variable–range hopping transport of flux lines is considerably reduced with respect to the non– interacting case, the effective Mott exponent being enhanced from p₀ = 1/3 to p_eff ≈ 0 .5 for this specific experiment.