UPPER CRITICAL-FIELD AND DENSITY-OF-STATES OF D-WAVE SUPERCONDUCTORS

The upper critical field and the density of states of d(x)2-y2-wave su perconductor in the vortex state are determined. The temperature depen dence of the upper critical field of d-wave superconductor without Pau li term appears to be consistent with the one observed in YBCO. Except in the immediate vicinity of T(c) (T greater-than-or-equal-to 0.88T(c )) a square vortex lattice tilted by 45-degrees from the a-axis is mor e favored than a triangular lattice. If we extrapolate the present den sity of states in the low-field region (B much-lesser-than H(c)2 (T)), we obtain the residual density of states proportional to (B)1/2 consi stent with an earlier Volovik's analysis.