ENERGY-GAP IN SUPERCONDUCTORS WITH SINGULAR ASYMMETRIC DENSITY OF STATES

The ratio R=2-DELTA-0/kT(c) is calculated for delta-function singularities in the density of states. Both symmetric and asymmetric densities of states are considered. In accordance with the symmetric powerlike singularities [D.C. Mattis and M. Molina, Phys. Rev, B 44, 12 565 (1991)], it is shown that neither the symmetric nor the asymmetric singularities in the density of states can explain those experimentally observed values in high-T(c) superconductors that are much higher than the BCS value of 3.52 in the weak-coupling limit.