Spinless fermion ladders at half filling - art. no. 045121

We study a half-filled ladder of spinless fermions. We show that contrary t o a single chain, the ladder becomes a Mott insulator for arbitrarily small repulsive interactions. We obtain the full phase diagram and physical quan tities such as the charge gap. We show that there is only a single insulati ng phase for repulsive interactions, regardless of the strength of the inte rchain hopping and single chain Mott gap. There is thus no confinement-deco nfinement transition in this system but a simple crossover. Using bosonizat ion with the renormalization group we show that upon doping the system beco mes a Luttinger liquid with a universal parameter K = 1/2 different from th e one of the single chain (K = 1/4).