We theoretically study the disorder-induced smearing of the density of states in a two-dimensional electron system, taking into account a spin-orbit term in the Hamiltonian of a free electron. We show that the characteristic energy scale for the smearing increases with increasing spin-orbit coupling. We also demonstrate that in the limit of a strong spin-orbit coupling the diagrams with self-intersections make a parametrically small contribution to the self-energy. As a result, the coherent potential approximation becomes asymptotically exact in this limit. The tail of the density of states has an energy scale which is much smaller than the magnitude of the smearing. We find the shape of the tail using the instanton approach.

• Received 10 February 1998

DOI:https://doi.org/10.1103/PhysRevB.58.6736