Finite-temperature properties of the Hubbard chain with bond-charge interaction

We investigate the one-dimensional Hubbard model with an additional bond-charge interaction, recently considered in the description of compounds that exhibit strong 1D features above the temperature of ordered phases. The partition function of the model is exactly calculated for a value of the bond-charge coupling; the behavior of the specific heat and spin susceptibility as a function of temperature is derived at arbitrary filling, and particularly discussed across the occurring metal-insulator transition. The results show that the bond-charge terms weaken the spin excitations of the system.Comment: 5 pages, 3 eps figure

Switching the sign of Josephson current through Aharonov-Bohm interferometry

We investigate the DC Josephson effect in a superconductor-normal metal-superconductor junction where the normal region consists of a ballistic ring. We show that a fully controllable $\pi$-junction can be realized through the electro-magnetostatic Aharonov-Bohm effect in the ring. The sign and the magnitude of the supercurrent can be tuned by varying the magnetic flux and the gate voltage applied to one arm, around suitable values. The implementation in a realistic set-up is discussed.Comment: 4 pages, 3 figure

Erratum to: Confinement versus interface bound states in spin-orbit coupled nanowires (The European Physical Journal Plus, (2020), 135, 7, (597), 10.1140/epjp/s13360-020-00614-2)

During production mistakes have been introduced

Strongly Interacting Luttinger Liquid and Superconductivity in an Exactly Solvable Model

A new family of exactly solvable one dimensional models with a hard-core repulsive potential is solved by the Bethe Ansatz for an arbitrary hard-core radius. The exact ground state phase diagrams in a plane 'electron density - on-site interaction' have been studied for several values of a hard-core radius. It is shown that superconducting phase and strongly interacting Luttinger liquid state are coexisted at a high electron density and unusually high value of repulsive on-site Coulomb interaction.Comment: 4 pages, 2 figures, RevTe

Band and filling controlled transitions in exactly solved electronic models

We describe a general method to study the ground state phase diagram of electronic models on chains whose extended Hubbard hamiltonian is formed by a generalized permutator plus a band-controlling term. The method, based on the appropriate interpretation of Sutherland's species, yields under described conditions a reduction of the effective Hilbert space. In particular, we derive the phase diagrams of two new models; the first one exhibits a band-controlled insulator-superconductor transition at half-filling for the unusually high value $U_c=6 t$; the second one is characterized by a filling-controlled metal-insulator transition between two finite regions of the diagram.Comment: 5 pages, REVTEX, 2 eps figure

Electron tunneling into a quantum wire in the Fabry-Perot regime

We study a gated quantum wire contacted to source and drain electrodes in the Fabry-Perot regime. The wire is also coupled to a third terminal (tip), and we allow for an asymmetry of the tip tunneling amplitudes of right and left moving electrons. We analyze configurations where the tip acts as an electron injector or as a voltage-probe, and show that the transport properties of this three-terminal set-up exhibit very rich physical behavior. For a non-interacting wire we find that a tip in the voltage-probe configuration affects the source-drain transport in different ways, namely by suppressing the conductance, by modulating the Fabry-Perot oscillations, and by reducing their visibility. The combined effect of electron electron interaction and finite length of the wire, accounted for by the inhomogeneous Luttinger liquid model, leads to significantly modified predictions as compared to models based on infinite wires. We show that when the tip injects electrons asymmetrically the charge fractionalization induced by interaction cannot be inferred from the asymmetry of the currents flowing in source and drain. Nevertheless interaction effects are visible as oscillations in the non-linear tip-source and tip-drain conductances. Important differences with respect to a two-terminal set-up emerge, suggesting new strategies for the experimental investigation of Luttinger liquid behavior.Comment: 27 pages, 10 figure

Nanotransformation and current fluctuations in exciton condensate junctions

We analyze the nonlinear transport properties of a bilayer exciton condensate that is contacted by four metallic leads by calculating the full counting statistics of electron transport for arbitrary system parameters. Despite its formal similarity to a superconductor the transport properties of the exciton condensate turn out to be completely different. We recover the generic features of exciton condensates such as counterpropagating currents driven by excitonic Andreev reflections and make predictions for nonlinear transconductance between the layers as well as for the current (cross)correlations and generalized Johnson-Nyquist relationships. Finally, we explore the possibility of connecting another mesoscopic system (in our case a quantum point contact) to the bottom layer of the exciton condensate and show how the excitonic Andreev reflections can be used for transforming voltage at the nanoscale.Comment: 5 pages, 4 figures, accepted by PR

Correlation length and the scaling parameter in the Renormalization Group

The basic procedure of renormalization group theory is used to split the free energy into a Kadanoff block formation part, and a renormalized block-block interaction part. The study of this redistribution as a function of the scaling parameter s shows that there is a stationarity value s* of s, which turns out to have the same critical behavior as the correlation length. It is suggested that s* can be used as an appropriate measure and definition of the correlation length, even for noncritical regions. The calculation of s* is thereby performed explicitly for the Gaussian, and numerically for the S4 model. A sharp separation between noncorrelated and correlated regimes is also found for the Gaussian model, well above the critical temperature. For the S4 model, the results suggest that ξ is characterized by a high-temperature Gaussian branch and by a genuine S4 branch at low temperatures, connected by a "plateau" in the intermediate region

Role of the equilibrium size of Kadanoff blocks in the loop-expansion technique

A method developed by the present authors in a previous paper [Phys. Rev. E 57, 2594 (1998)] leads to the introduction of the equilibrium size of the Kadanoff blocks as a useful tool to approach the critical properties of the φ4 model. The present paper aims to elucidate the role of the equilibrium size of the Kadanoff blocks in the loop-expansion technique currently used in the field-theoretic renormalization. While the standard results are readily obtained, aspects emerge that help clarify the true nature of the smallness parameter in the loop-expansion technique

Signature of interaction in dc transport of ac gated Quantum Spin Hall edge states

In the presence of a scattering potential, electron transport in a quantum wire is known to be dramatically modified by backward scattering and unaffected by forward scattering processes. We show that the scenario is quite different in Quantum Spin Hall effect edge states coupled at a constriction. The helical nature of these states leads to the appearance of a forward scattering spin channel that is absent in other Luttinger liquid realizations. Suitably applied ac gate voltages can thus operate on the spin of electrons tunneling across the constriction, and induce in the dc tunneling current a cusp pattern that represents the signature of the edge state electronic interaction.Comment: 4 pages, 2 Figure