Electric field induced memory and aging effects in pure solid N_2
  We report combined high sensitivity dielectric constant and heat capacity measurements of pure solid N_2 in the presence of a small external ac electric field in the audio frequency range. We have observed strong field induced aging and memory effects which show that field cooled samples may be prepared in a variety of metastable states leading to a free energy landscape with experimentally ``tunable'' barriers, and tunneling between these states may occur within laboratory time scales. 
S. Pilla, J. A. Hamida, K. A. Muttalib, and N. S. Sullivan