Dynamical localization in a chain of hard core bosons under a periodic driving

We study the dynamics of a one-dimensional lattice model of hard core bosons which is initially in a superfluid phase with a current being induced by applying a twist at the boundary. Subsequently, the twist is removed and the system is subjected to periodic \de-function kicks in the staggered on-site potential. We present analytical expressions for the current and work done in the limit of an infinite number of kicks. Using these, we show that the current (work done) exhibit a number of dips (peaks) as a function of the driving frequency and eventually saturates to zero (a finite value) in the limit of large frequency. The vanishing of the current (and the saturation of the work done) can be attributed to a dynamic localization of the hard core bosons occurring as a consequence of the periodic driving. Remarkably, we show that for some specific values of the driving amplitude, the localization occurs for any value of the driving frequency. Moreover, starting from a half-filled lattice of hard core bosons with the particles localized in the central region, we show that the spreading of the particles occurs in a light-cone-like region with a group velocity that vanishes when the system is dynamically localized.Comment: 5 pages, and 3 figures. Accepted for publication in PR

Nonequilibrium charge transport in an interacting open system: two-particle resonance and current asymmetry

We use Lippman-Schwinger scattering theory to study nonequilibrium electron transport through an interacting open quantum dot. The two-particle current is evaluated exactly while we use perturbation theory to calculate the current when the leads are Fermi liquids at different chemical potentials. We find an interesting two-particle resonance induced by the interaction and obtain criteria to observe it when a small bias is applied across the dot. Finally, for a system without spatial inversion symmetry we find that the two-particle current is quite different depending on whether the electrons are incident from the left lead or the right lead.Comment: 5 pages, 2 figures; made some major changes -- this is the published versio

Scattering of electrons from an interacting region

We address the problem of transmission of electrons between two noninteracting leads through a region where they interact (quantum dot). We use a model of spinless electrons hopping on a one-dimensional lattice and with an interaction on a single bond. We show that all the two-particle scattering states can be found exactly. Comparisons are made with numerical results on the time evolution of a two-particle wave packet and several interesting features are found for scattering. For N particles the scattering state is obtained by perturbation theory. For a dot connected to Fermi seas at different chemical potentials, we find an expression for the change in the Landauer current resulting from the interactions on the dot. We end with some comments on the case of spin-1/2 electrons.Comment: 5 pages including 2 figures; this is the final version published in Physical Review Letter

Percutaneous computed tomography-guided core biopsy for the diagnosis of mediastinal masses

Aim : To describe various approaches of computed tomography (CT)-guided core biopsy and evaluate its ability to obtain adequate tissue for the assessment of mediastinal masses. Materials and Methods : Between February 2004 and October 2006, 83 percutaneous CT-guided biopsies of mediastinal lesions were performed on 82 patients under local anesthesia. Coaxial needles were used and minimum of 3-4 cores were obtained. Post-biopsy CT scan was performed and patients observed for any complications. Tissue samples were taken to Pathology Department in formalin solution. Results : From the 83 biopsies, adequate tissue for histological diagnosis was obtained in 80 (96%), and the biopsy was considered diagnostic. Of the 80 diagnostic biopsies, 74 biopsy samples were definitive for neoplastic pathology and 6 biopsy samples revealed no evidence of malignancy. There were no major complications. Minor complications were recorded in 5 patients. Conclusion : Percutaneous image-guided core biopsy of mediastinal lesions is an accurate, safe and cost-effective tool for the initial assessment of patients with mediastinal masses