arXiv subjects

Alexander Moreno

Publications and source records attributed to Alexander Moreno.

20 records · Page 2Linked to original sources

arXiv2013

Transport through two interacting resonant levels connected by a Fermi sea

We study transport at finite bias, i.e. beyond the linear regime, through two interacting resonant levels connected by a Fermi sea, by means of time-dependent density matrix renormalization group. We first consider methodological issues, like the protocol that leads to a current-currying state and the characterization of the steady state. At finite sizes both the current and the occupations of the interacting levels oscillate as a function of time. We determine the amplitude and period of such oscillations as a function of bias. We find that the occupations on the two dots oscillate with a relative phase which depends on the distance between the impurities and on the Fermi momentum of the Fermi sea, as expected for RKKY interactions. Also the approximant to the steady-state current displays oscillations as a function of the distance between the impurities. Such a behavior can be explained by resonances in the free case. We then discuss the incidence of interaction on such a behavior. We conclude by showing the effect of the bias on the current, making connection with the one-impurity case.

cond-mat.str-el↗

arXiv2011

Ground-State Phase Diagram of the 1D t-J model

We examine the ground-state phase diagram of the t-J model in one dimension by means of the Density Matrix Renormalization Group. This model is characterized by a rich phase diagram as a function of the exchange interaction J and the density n, displaying Luttinger-liquid (LL) behavior both of repulsive and attractive (i.e. superconducting) nature, a spin-gap phase, and phase-separation. The phase boundaries separating the repulsive from the attractive LL phase as J is increased, and also the boundaries of the spin-gap region at low densities, and phase-separation at even larger J, are determined on the basis of correlation functions and energy-gaps. In particular, we shed light on a contradiction between variational and renormalization-group (RG) results about the extent of the spin-gap phase, that results larger than the variational but smaller than the RG one. Furthermore, we show that the spin gap can reach a sizable value (~ 0.1 t) at low enough filling, such that preformed pairs should be observable at temperatures below these energy scales. No evidence for a phase with clustering of more than two particles is found on approaching phase separation.

cond-mat.str-el↗