Orbital antiferromagnetic currents in a frustrated fermionic ladder

Abstract: We consider a spinless $t$-$t'$ ionic Hubbard chain at 1/2 filling and large hopping ratio $t'/t$. In this limit the model adequately maps onto a weakly coupled triangular ladder with a potential interchain bias. The low-energy properties of the system are formed due to the interplay of geometrical frustration, correlations and charge imbalance. We derive the effective field-theoretical model to study universal properties of the model in the scaling limit. We show that at full dynamical frustration the ground state of the ladder represents a repulsive version of the Luther-Emery liquid with dominant orbital antiferromagnetic correlations exhibiting the slowest power-law decay in the ground state. Pairing correlations also display algebraic order but are subdominant. At an incomplete dynamical frustration a finite commensurability gap is dynamically generated, and the fluctuating OAF transforms to a long-range ordered state with a spontaneously broken time reversal symmetry. The mass gap in the spectrum of relative density fluctuations gets suppressed upon increasing the potential bias.