Bloch's theorem A Bloch wave or Bloch state,named after Felix Bloch. is the wavefunction of a particle (usually,an electron) placed in a periodic potential.Bloch's theorem states that the energy eigenfunction for such a system may be written as the product of a plane wave envelope function and a periodic function (periodic Bloch function)that has the same periodicity as the potential: w(x)=e.Φk(x), Φx(x+a)=Φx(x).Bloch’s theorem A Bloch wave or Bloch state, named after Felix Bloch, is the wavefunction of a particle (usually, an electron) placed in a periodic potential. Bloch's theorem states that the energy eigenfunction for such a system may be written as the product of a plane wave envelope function and a periodic function (periodic Bloch function) that has the same periodicity as the potential: (x) e (x), K iKx    (x a) (x). K   K