Critical behaviour of ($2+1$)-dimensional QED: 1/N_f-corrections in the   Landau gauge
  The dynamical generation of a fermion mass is studied within ($2+1$)-dimensional QED with $N$ four-component fermions in the leading and next-to-leading orders of the 1/N expansion. The analysis is carried out in the Landau gauge which is supposed to insure the gauge independence of the critical fermion flavour number, N_c. It is found that the dynamical fermion mass appears for N<N_c where N_c=3.29, that is only about $1\%$ larger than its value at leading order. 
A. V. Kotikov, V. I. Shilin and S. Teber
hep-th cond-mat.mes-hall