Generation and control of resonance states in crossed magnetic and   electric fields
  A two-dimensional electron system interacting with an impurity and placed in crossed magnetic and electric fields is under investigation. Since it is assumed that an impurity center interacts as an attractive $\delta$-like potential a renormalization procedure for the retarded Green's function has to be carried out. For the vanishing electric field we obtain a close analytical expression for the Green's function and we find one bound state localized between Landau levels. It is also shown by numerical investigations that switching on the electric field new long-living resonance states localized in the vicinity of Landau levels can be generated. 
Katarzyna Krajewska and Jerzy Z. Kaminski