Spontaneous photon emission from a semiconductor
  Semiconductor's energy band and its degeneracy are altered when an external magnetic field varies, analogously to the appearance of Landau levels. Such alternation leads to the variation of energy levels and thus quantum-mechanical instability. As a consequence, spontaneous photon emission and/or paramagnetically screening effect take place. By computing total energy variation, we discuss why these effects are bound to occur. In addition, we calculate the rate and spectrum of spontaneous photon emission, which can be experimentally tested. 
She-Sheng Xue