Functional methods in the theory of magnetoimpurity states of electrons   in quantum wires
  Functional methods are used to study magnetoimpurity states of electrons in nanostructures. The Keldysh formalism is applied to these states. The theory is illustrated using a quantum wire sample with impurity atoms capable of localizing electrons in a magnetic field. The characteristics of magnetoimpurity states of electrons in the wire are calculated using the model of a Gaussian separable potential. 
A. M. Ermolaev, G. I. Rashba