Dynamical properties of doped strongly coupled Hubbard chains

Using grand-canonical quantum Monte-Carlo (QMC) simulations combined with maximum entropy (MaxEnt) analytic continuation, as well as analytical methods, we examine the one- and two-particle dynamical properties of the Hubbard model on two coupled chains at small doping. For large values of the interchain coupling t(perpendicular to) greater than or similar to 2t the local rung approximation (LRA) developed for the half-filled case describes the high-energy features of the system. In addition, in the bonding charge channel a pronounced gapless mode is observed, which indicates the insulator-metal transition. The main features of the quasi-particle dispersion are found unchanged (''rigid-band like'') when going to smaller (isotropic) couplings and intermediate dopings.