Friday, 28 April 2017

quantum mechanics - Momentum $k$-space Brillouin zone for non-quadratic and interacting systems?


Usually, we define the momentum $k$-space Brillouin zone (by Fourier transformed from the real space $x$ with a wavefunction $\psi(x)$ to the momentum $k$-space) for:


(1) quadratic non-interacting (free) systems (such as those can be written in terms of BdG equation.)


and


(2) translational invariant systems (so one can define the conjugate momentum $k$ as a good quantum number).



Question: Could we define the momentum $k$-space Brillouin zone for


non-quadratic and interacting systems


but translational invariant systems? (Namely can we modify (1) to interacting, but keep (2)?)






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