Singularity of the Vortex Density of States in d-wave Superconductors
  In d-wave superconductors, the electronic density of states (DOS) induced by a vortex exhibits 1/|E| divergency at low energies. It is the result of gap nodes in the excitations spectrum outside the vortex core. The heat capacity in two regimes, (T/T_c)^2 >> B/B_{c2} and (T/T_c)^2 << B/B_{c2}, is discussed. 
N.B. Kopnin and G.E. Volovik