Ho<Subscript>0.1</Subscript>Ca<Subscript>0.9</Subscript>MnO<Subscript>3</S ubscript> is a canted antiferromagnet with the magnetic space group Pn′ma′. The magnetic structure is a superposition C<Subscript> x </Subscript>F<Subscript> y </Subscript>A<Subscript> z </Subscript> of the three types of order allowed in Pn′ma′. In the Ca-rich corner of the system Ho<Subscript>1−x </Subscript>Ca<Subscript> x </Subscript>MnO<Subscript>3</Subscript> the title compound has a strong magnetoelastic...</subscript></subscript></subscript></subscript></subscript></subscript><//s></subscript></subscript></subscript>

We study the one-dimensional Holstein model of spinless fermions interacting with dispersion-less phonons by using a recently developed projector-based renormalization method (PRM). At half-filling the system shows a metal-insulator transition to a Peierls distorted state at a critical...

We present a non-perturbative study of an extended Falicov-Kimball model in one dimension. Working within the binary alloy interpretation, we include the spin of the itinerant electrons and a Hubbard interaction to model the inter-electron correlations. We derive an effective Ising model for the...

An analysis of Luttinger's theorem shows that – contrary to recent claims – it is not valid for a generic Mott insulator. For a two-orbital Hubbard model with two electrons per site the crossover from a non-magnetic correlated insulating phase (Mott or Kondo insulator) to a band insulator is...