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

“If It Is Written by Allah, There Is Nothing That Can Stop It”: Saudi women’s breast cancer narratives

The purpose of this study was to identify cultural models of breast cancer held by Saudi women and to explore how these may influence early detection and treatment-seeking behaviors. Data were collected via semi-structured interviews with breast cancer survivors (n=20) from two Western cities in Saudi Arabia. Respondents were recruited through social networking, using purposive, snowball sampling. Illness narratives elicited during interviews were transcribed, coded and then analyzed using a modified grounded theory approach. Results suggest that fatalism, perceived threats to traditional role fulfillment, and a preference for traditional therapies commonly mark the breast cancer experiences of Saudi women, influencing their early detection and treatment-seeking behaviors. A more nuanced understanding of emic viewpoints could help to improve public health messaging and intervention strategies in Saudi Arabia

Detection of Tiny Mechanical Motion by Means of the Ratchet Effect

We propose a position detection scheme for a nanoelectromechanical resonator based on the ratchet effect. This scheme has an advantage of being a dc measurement. We consider a three-junction SQUID where a part of the superconducting loop can perform mechanical motion. The response of the ratchet to a dc current is sensitive to the position of the resonator and the effect can be further enhanced by biasing the SQUID with an ac current. We discuss the feasibility of the proposed scheme in existing experimental setups.Comment: 8 pages, 9 figure

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

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

Exact thermodynamics of an Extended Hubbard Model of single and paired carriers in competition

By exploiting the technique of Sutherland's species, introduced in \cite{DOMO-RC}, we derive the exact spectrum and partition function of a 1D extended Hubbard model. The model describes a competition between dynamics of single carriers and short-radius pairs, as a function of on-site Coulomb repulsion ($U$) and filling ($\rho$). We provide the temperature dependence of chemical potential, compressibility, local magnetic moment, and specific heat. In particular the latter turns out to exhibit two peaks, both related to `charge' degrees of freedom. Their origin and behavior are analyzed in terms of kinetic and potential energy, both across the metal-insulator transition point and in the strong coupling regime.Comment: 14 pages, 15 eps figure

“If It Is Written by Allah, There Is Nothing That Can Stop It”: Saudi women’s breast cancer narratives

The purpose of this study was to identify cultural models of breast cancer held by Saudi women and to explore how these may influence early detection and treatment-seeking behaviors. Data were collected via semi-structured interviews with breast cancer survivors (n=20) from two Western cities in Saudi Arabia. Respondents were recruited through social networking, using purposive, snowball sampling. Illness narratives elicited during interviews were transcribed, coded and then analyzed using a modified grounded theory approach. Results suggest that fatalism, perceived threats to traditional role fulfillment, and a preference for traditional therapies commonly mark the breast cancer experiences of Saudi women, influencing their early detection and treatment-seeking behaviors. A more nuanced understanding of emic viewpoints could help to improve public health messaging and intervention strategies in Saudi Arabia

Blockade and Counterflow Supercurrent in exciton-condensate Josephson junctions

We demonstrate that perfect conversion between charged supercurrents in superconductors and neutral supercurrents in electron-hole pair condensates is possible via a new Andreev-like scattering mechanism. As a result, when two superconducting circuits are coupled through a bilayer exciton condensate, the superflow in both layers is drastically modified. Depending on the phase biases the supercurrents can be completely blocked or exhibit perfect drag.Comment: 4 pages, 2 figure

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