arXiv subjects

Vito Marino

Publications and source records attributed to Vito Marino.

6 recordsLinked to original sources

arXiv2026

Influence of the inter-orbital interaction and kinetic terms on superconductivity: a simple two-orbital Hubbard model

We investigate a minimal two-orbital Hubbard model with intra- and inter-orbital nearest-neighbor hopping $t$ and $\tilde{t}$, as well as intra- and inter-orbital density-density interactions $U$ and $U'$ by means of variational ansätze based on Jastrow-Slater wave functions within quantum Monte Carlo techniques. To focus on the electronic mechanisms of superconductivity, we restrict the variational ansätze to uniform nonmagnetic states with an explicit pairing amplitude and compute the pairing correlations as a function of filling and model parameters. At $U/t=10$, superconducting correlations are highly enhanced by the presence of inter-orbital terms, $U'$ and $\tilde{t}$. For $\tilde{t}=0$, a finite value of $U'$ effectively screens the intra-orbital repulsion $U$, producing a shift in the superconducting dome. Consequently, inter-orbital repulsion yields a sizable increase in electron pairing compared to the single-orbital baseline. Furthermore, introducing a finite $\tilde{t}$ provides an additional boost to superconducting correlations, an effect driven by the simultaneous presence of flat and broad bands in the electronic structure.

cond-mat.str-el↗

arXiv2026

Variational Monte Carlo study of a two-orbital Hubbard model for the iron pnictides

We study a two-orbital Hubbard-Kanamori model, which has been originally proposed for iron-based superconductors, using variational Monte Carlo. We span the nonmagnetic sector at both hole-doping and electron-doping, with respect to the half-filled case $n=2$. We report the presence of a superconductive region with a $s^{\pm}$ symmetry only when the half-filled system is in a Mott state, while orbital selectivity is absent. These results are qualitatively different from what was reported in the three-orbital Hubbard-Kanamori model, where a more extended superconductive region was observed with a concomitant development of orbital selectivity, and they are to some extent more reminiscent of the single-band Hubbard model.

cond-mat.str-el↗

arXiv2025

Intertwined superconductivity and orbital selectivity in a three-orbital Hubbard model for the iron pnictides

We study a three-orbital Hubbard-Kanamori model relevant for iron-based superconductors using variational wave functions explicitly including spatial correlations and electron pairing. We span the nonmagnetic sector from filling $n=4$, which is representative of undoped iron-based superconductors, to $n=3$, where a Mott insulating state with each orbital at half filling is found. In the strong-coupling regime, when the electron density is increased, we find a spontaneous differentiation between the occupation of $d_{xz}$ and $d_{yz}$ orbitals, leading to an orbital-selective state with a nematic character that becomes stronger at increasing density. One of these orbitals stays half-filled for all densities while the other one hosts (together with the $d_{xy}$ orbital) the excess of electron density. Most importantly, in this regime long-range pairing correlations appear in the orbital with the largest occupation. Our results highlight a strong link between orbital-selective correlations, nematicity, and superconductivity, which requires the presence of a significant Hund's coupling.

cond-mat.str-el↗

arXiv2024

Variational Monte Carlo study of stripes as a function of doping in the $t-t'$ Hubbard model

We perform variational Monte Carlo simulations of the single-band Hubbard model on the square lattice with both nearest ($t$) and next-nearest ($t'$) neighbor hoppings. Our work investigates the consequences of increasing hole doping on the instauration of stripes and the behavior of the superconducting order parameter, with a discussion on how the two phenomena affect each other. We consider two different values of the next-nearest neighbor hopping parameter, that are appropriate for describing cuprate superconductors. We observe that stripes are the optimal state in a wide doping range; the stripe wavelength reduces at increasing doping, until stripes melt into a uniform state for large values of doping. Superconducting pair-pair correlations, indicating the presence of superconductivity, are always suppressed in the presence of stripes. Our results suggest that the phase diagram for the single-band Hubbard model is dominated by stripes, with superconductivity being possible only in a narrow doping range between striped states and a nonsuperconducting metal.

cond-mat.str-el↗

arXiv2022

Stripes in the extended $t-t^\prime$ Hubbard model: A Variational Monte Carlo analysis

By using variational quantum Monte Carlo techniques, we investigate the instauration of stripes (i.e., charge and spin inhomogeneities) in the Hubbard model on the square lattice at hole doping $δ=1/8$, with both nearest- ($t$) and next-nearest-neighbor hopping ($t^\prime$). Stripes with different wavelengths $λ$ (denoting the periodicity of the charge inhomogeneity) and character (bond- or site-centered) are stabilized for sufficiently large values of the electron-electron interaction $U/t$. The general trend is that $λ$ increases going from negative to positive values of $t^\prime/t$ and decreases by increasing $U/t$. In particular, the $λ=8$ stripe obtained for $t^\prime=0$ and $U/t=8$ [L.F. Tocchio, A. Montorsi, and F. Becca, SciPost Phys. {\bf 7}, 21 (2019)] shrinks to $λ=6$ for $U/t\gtrsim 10$. For $t^\prime/t<0$, the stripe with $λ=5$ is found to be remarkably stable, while for $t^\prime/t>0$, stripes with wavelength $λ=12$ and $λ=16$ are also obtained. In all these cases, pair-pair correlations are highly suppressed with respect to the uniform state (obtained for large values of $|t^\prime/t|$), suggesting that striped states are not superconducting at $δ=1/8$.

cond-mat.str-el↗

arXiv2021

Flux pumping of Cooper pairs through a Josephson Energy-Suppression Pump

In this paper, we propose a novel kind of Josephson-Energy Suppression Pump (JESP) controlled by a fully magnetic flux drive. The device presented here is composed of two superconducting loops interrupted at one side by superconducting nanowires which are joined together by a superconducting island. The phase difference developed at the edges of the nanowires by means of the magnetic flux threading the loops can collapse their Cooper condensates, leading to complete suppression of the Josephson energies. This mechanism allows to greatly reduce the leakage current when performing Cooper pair pumping by a pure magnetic pumping cycle without involving any gate modulation. The pumping capability of the JESP is studied through a master equation approach in the non-adiabatic case.

cond-mat.supr-con↗