arXiv subjects

Marco Uguccioni

Publications and source records attributed to Marco Uguccioni.

4 recordsLinked to original sources

arXiv2025

Transport properties and thermopower of the spinful Sachdev-Ye-Kitaev dot

We study the electric and thermoelectric transport through a spinful complex Sachdev-Ye-Kitaev (SYK) quantum dot coupled to metallic leads, forming a N-SYK-N junction, by the Keldysh field theory approach. Unlike traditional equilibrium approaches, our formulation treats the system as an open, interacting quantum conductor under non-equilibrium conditions, without resorting to the replica trick. Starting from the exact Keldysh-Dyson equations, we derive analytical results for the tunneling and zero-temperature limits and perform a numerical analysis in the linear-response regime. We characterize the dependence of conductance, thermoelectric coefficient, and Seebeck effect on the particle-hole asymmetry parameter and coupling strength to the leads. Our results reveal distinctive non-Fermi liquid signatures of the SYK model in transport properties and identify coupling regimes where thermoelectric effects are enhanced, suggesting experimentally accessible fingerprints of SYK physics in mesoscopic systems.

cond-mat.str-el↗

arXiv2025

Keldysh field theory approach to direct electric and thermoelectric currents in quantum dots coupled to superconducting leads

We study the transport properties of a quantum dot contacted to two superconducting reservoirs by means of the Keldysh field theory approach, showing how this technique allows us to straightforwardly recover previous results, resulting extremely effective in dealing with quantum transport problems. In particular, we determine the direct current occurring at equilibrium and the electric and thermoelectric currents triggered when the system is driven out of equilibrium by a voltage or a temperature bias, also for a normal-quantum dot-superconductor junction. The main result of the work is the derivation of the full expression for the thermoelectric current in a superconductor-quantum dot-superconductor junction for any values of the temperature difference between the superconducting leads. We show that in the linear response regime, in addition to the Josephson current, a weakly phase-dependent thermoelectric contribution occurs, provided that electron-hole symmetry is broken. Far from linearity, instead, other contributions arise which lead to thermoelectric effects, dominant at weak coupling, also in the presence of particle-hole symmetry.

cond-mat.mes-hall↗

arXiv2024

Keldysh field theory approach to electric and thermoelectric transport in quantum dots

We compute the current and the noise power matrix in a quantum dot connected to two metallic reservoirs by using the Keldysh field theory approach, a non-equilibrium quantum field theory language in the functional integral formalism. We first show how this technique allows us to recover rapidly and straightforwardly well-known results in literature, such as the Meir-Wingreen formula for the average current, resulting extremely effective in dealing with quantum transport problem. We then discuss in detail the electric and thermoelectric properties due to transport of electrons in the case of a single-level and two-level non-interacting quantum dot. In particular, we derive the optimal conditions for maximizing the thermoelectric current, finding an upper limit for the thermoelectric coefficient. Moreover, in the two-level system we show that the zero-temperature linear conductance drops rapidly to zero by a symmetrical removal of the degeneracy at the Fermi energy.

cond-mat.mes-hall↗

arXiv2023

Normal and superconducting currents through the Sachdev-Ye-Kitaev model

We study the current driven by an applied voltage as a function of time through the Sachdev-Ye-Kitaev model when coupled to two normal or superconducting reservoirs. For normal leads, in the strong coupling limit and for small bias, the current through the Sachdev-Ye-Kitaev model, described by a quartic interaction term, reaches monotonically the stationarity, in contrast to the case of a disordered quadratic interaction where the current has a peak before reaching the stationary phase. For superconducting leads the currents have oscillations whose frequencies are determined by the gap and the voltage, and are suppressed in the strong coupling limit. Moreover, due to different short time scales between the normal and the oscillating part of the superconducting current, a peak appears before reaching the stationarity.

cond-mat.str-el↗