METAL
Mott-Hubbard: for U ≪ W, the system is a metal (Fermi liquid). As U/W increases past ~2.5 (half-filling),
the DOS splits into lower Hubbard band (LHB) and upper Hubbard band (UHB) separated by a gap ~ U − W.
The quasiparticle (QP) peak at E_F carries weight Z = 1 − (U/U_c)² → 0 at the Mott transition.
DMFT captures three-peak structure: LHB + QP peak + UHB. Mott gap opens at U_c ≈ 2.5t·√D.