Ground state of a chemically modulated Hubbard chain at half filling - art. no. 125113

We have studied the Hubbard chain with a periodic variation of the site pot ential for the half-filled band by using a real space renormalization group (RG) method complemented by a mean-field analysis. The ground state phase diagram shows a transition between a charge density wave (CDW) and a spin d ensity wave (SDW). The energy gap and the local moment, as obtained from th e RG, clearly identify the phase transition in agreement with the RG flow p attern. Within the mean-field approximation (MFA the charge and spin order parameters are calculated to trace out the transition. The phase diagram ob tained by the RG calculation shows excellent agreement with that obtained b y the MFA especially in the weak- to intermediate-coupling region. We have also calculated the Drude weight (within the MFA) to analyze the conductivi ty of such a chain of finite length. The Drude weight also captures some in teresting features of the competition between the SDW and the CDW.