Quasiperiodic hubbard chains

Low-energy properties of half-filled Fibonacci Hubbard models are studied b y weak-coupling renormalization group and density matrix renormalization gr oup methods. In the case of diagonal modulation, weak Coulomb repulsion is irrelevant and the system behoves as a free Fibonacci chain, while for stro ng Coulomb repulsion the charge sector becomes a Mott insulator and the spi n sector behaves as a uniform Heisenberg antiferromagnetic chain. The off-d iagonal modulation always drives the charge sector to a Mott insulator and the spin sector to a Fibonacci antiferromagnetic Heisenberg chain.