COULOMB GAP AND CORRELATED VORTEX PINNING IN SUPERCONDUCTORS

The positions of columnar pins and magnetic flux lines determined from a decoration experiment on Bi2Sr2CaCu2O8 were used to calculate the distribution of pinning energies in the Bose glass phase. A wide Coulomb gap is found, with effective gap exponent seff1.2, as a result of interactions between the vortices. As a consequence, the variable-range hopping transport of flux lines is considerably reduced with respect to the noninteracting case, the effective Mott exponent being enhanced from p0=1/3 to peff0.5 for this sample. © 1995 The American Physical Society.