Magnetic Quantum Wire as a Spin Filter: An Exact Study

We propose that a magnetic quantum wire composed of magnetic and non-magnetic atomic sites can be used as a spin filter for a wide range of applied bias voltage. We adopt a simple tight-binding Hamiltonian to describe the model where the quantum wire is attached to two semi-infinite one-dimensional non-magnetic electrodes. Based on single particle Green's function formalism all the calculations are performed numerically which describe two-terminal conductance and current through the wire. Our exact results may be helpful in fabricating mesoscopic or nano-scale spin filter.Comment: 6 pages, 5 figure

Magneto-transport in a binary alloy ring

Magneto-transport properties are investigated in a binary alloy ring subjected to an Aharonov-Bohm (AB) flux \phi within a single-band non-interacting tight-binding framework. In the first part, we expose analytically the behavior of persistent current in an isolated ordered binary alloy ring as functions of electron concentration N_e and AB flux \phi. While, in the second part of the article, we discuss electron transport properties through a binary alloy ring attached to two semi-infinite one-dimensional metallic electrodes. The effect of impurities is also analyzed. From our study we propose that under suitable choices of the parameter values the system can act as a p-type or an n-type semiconductor.Comment: 7 pages, 8 figure

Multi-terminal Electron Transport Through Single Phenalenyl Molecule: A Theoretical Study

We do parametric calculations to elucidate multi-terminal electron transport properties through a molecular system where a single phenalenyl molecule is attached to semi-infinite one-dimensional metallic leads. A formalism based on the Green's function technique is used for the calculations while the model is described by tight-binding Hamiltonian. We explore the transport properties in terms of conductance, reflection probability as well as current-voltage characteristic. The most significant feature we articulate is that all these characteristics are very sensitive to the locations where the leads are connected and also the molecule-to-lead coupling strengths. The presence of other leads also has a remarkable effect on these transport properties. We study these phenomena for two-, three- and four-terminal molecular systems. Our numerical study may be utilized in designing tailor-made molecular electronic devices.Comment: 13 pages, 15 figure

Quantum Transport in an Array of Mesoscopic Rings: Effect of Interface Geometry

Electron transport properties are investigated in an array of mesoscopic rings, where each ring is threaded by a magnetic flux $\phi$. The array is attached to two semi-infinite one-dimensional metallic electrodes, namely, source and drain, where the rings are considered either in series or in parallel configuration. A simple tight-binding model is used to describe the system and all the calculations are done based on the Green's function formalism. Here, we present conductance-energy and current-voltage characteristics in terms of ring-to-electrode coupling strength, ring-electrode interface geometry and magnetic flux. Most interestingly it is observed that, typical current amplitude in an array of mesoscopic rings in the series configuration is much larger compared to that in parallel configuration of those rings. This feature is completely different from the classical analogy which may provide an important signature in designing nano-scale electronic devices.Comment: 13 pages, 12 figure

Persistent currents with long-range hopping in 1D single-isolated-diffusive rings

We show from exact calculations that a simple tight-binding Hamiltonian with diagonal disorder and long-range hopping integrals, falling off as a power $\mu$ of the inter-site separation, correctly describes the experimentally observed amplitude (close to the value of an ordered ring) and flux-periodicity ($hc/e$) of persistent currents in single-isolated-diffusive normal metal rings of mesoscopic size. Long-range hopping integrals tend to delocalize the electrons even in the presence of disorder resulting orders of magnitude enhancement of persistent current relative to earliar predictions.Comment: 4 pages, 3 figure

Strange behavior of persistent currents in small Hubbard rings

We show exactly that small Hubbard rings exhibit unusual kink-like structures giving anomalous oscillations in persistent current. Singular behavior of persistent current disappears in some cases. In half-filled systems mobility gradually drops to zero with interaction, while it converges to some finite value in non-half-filled cases.Comment: 7 pages, 6 figure

On the role of electron correlation and disorder on persistent currents in isolated one-dimensional rings

To understand the role of electron correlation and disorder on persistent currents in isolated 1D rings threaded by magnetic flux $\phi$, we study the behavior of persistent currents in aperiodic and ordered binary alloy rings. These systems may be regarded as disordered systems with well-defined long-range order so that we do not have to perform any configuration averaging of the physical quantities. We see that in the absence of interaction, disorder suppresses persistent currents by orders of magnitude and also removes its discontinuity as a function of $\phi$. As we introduce electron correlation, we get enhancement of the currents in certain disordered rings. Quite interestingly we observe that in some cases, electron correlation produces kink-like structures in the persistent current as a function of $\phi$. This may be considered as anomalous Aharonov-Bohm oscillations of the persistent current and recent experimental observations support such oscillations. We find that the persistent current converges with the size of the rings.Comment: 9 pages, 8 figure