arXiv subjects

E. Arrigoni

Publications and source records attributed to E. Arrigoni.

57 records · Page 4Linked to original sources

arXiv1997

Electron transport in coupled chains of interacting fermions with impurities

We study the low-temperature transport of a doped two-chain ladder system of interacting fermions in the presence of a barrier or of a low concentration of impurities. Above a certain value of the interaction, the conductance is suppressed, like for a single chain, despite the presence of dominant superconducting correlations. There is, however, a region of repulsive interaction where perfect transmission across the barrier occurs unlike the single-chain case. We provide a possible explanation for the temperature maximum of the resistivity in the normal state of \srca.

cond-mat.str-el↗

arXiv1995

On an exact criterion for choosing the hopping operator in the four-slave-boson approach

We consider the $N$-component generalization of the four-slave-boson approach to the Hubbard model, where $1/N$ acts as the small parameter that controls the fluctuations about the saddle point, and address the problem of the appropriate choice of the bosonic hopping operator $z_{i\g}$. By suitably reorganizing the Fock space, we show that the square-root form for $z\is$ (originally introduced by Kotliar and Ruckenstein) reproduces the exact independent-fermion ($U=0$) results not only at the mean-field ($N=\infty$) level but also to {\evi all orders in the $1/N$ expansion}, provided one relaxes the usually adopted normal-ordered prescription for $z\is$. This ensures that $z\is$ needs not be modified at successive orders in the fluctuation expansion, and implies that all correlation functions are correctly recovered in the $U=0$ limit, a nontrivial result for the slave-boson approach. In addition, it provides a stringent requirement on the form of $z\is$, which might be also generalized to alternative slave-boson formalisms (like the spin-rotation-invariant formulation).

cond-mat↗

arXiv1995

On the correct continuum limit of the functional-integral representation for the four-slave-boson approach to the Hubbard model: Paramagnetic phase

The Hubbard model with finite on-site repulsion U is studied via the functional-integral formulation of the four-slave-boson approach by Kotliar and Ruckenstein. It is shown that a correct treatment of the continuum imaginary time limit (which is required by the very definition of the functional integral) modifies the free energy when fluctuation (1/N) corrections beyond mean-field are considered. Our analysis requires us to suitably interpret the Kotliar and Ruckenstein choice for the bosonic hopping operator and to abandon the commonly used normal-ordering prescription, in order to obtain meaningful fluctuation corrections. In this way we recover the exact solution at U=0 not only at the mean-field level but also at the next order in 1/N. In addition, we consider alternative choices for the bosonic hopping operator and test them numerically for a simple two-site model for which the exact solution is readily available for any U. We also discuss how the 1/N expansion can be formally generalized to the four-slave-boson approach, and provide a simplified prescription to obtain the additional terms in the free energy which result at the order 1/N from the correct continuum limit.

cond-mat↗