# Enhanced negative nonlocal conductance in an interacting quantum dot connected to two ferromagnetic leads and one superconducting lead

## TL;DR

This study explores how superconducting proximity effects and spin polarization influence electronic conductance in a quantum dot system connected to ferromagnetic and superconducting leads, revealing conditions for negative nonlocal conductance.

## Contribution

It introduces a detailed analysis of the interplay between Kondo correlations, superconductivity, and spin polarization in a three-terminal quantum dot device using advanced theoretical methods.

## Key findings

- Superconducting proximity suppresses local conductance by weakening the Kondo peak.
- When superconducting coupling exceeds normal lead coupling, cross conductance becomes negative.
- Spin polarization affects conductance differently in parallel and antiparallel configurations.

## Abstract

In this paper, we investigate the electronic transport properties of a quantum dot (QD) connected to two ferromagnetic leads and one superconductor lead in the Kondo regime by means of the finite-$U$ slave boson mean field approach and nonequilibrium Green function technique. In this three-terminal hybrid nano-device, we will focus our attention on the joint effects of the Konod correlation, superconducting proximity pairing, and spin polarization of leads. It is found that: the superconducting proximity effect will suppress the linear local conductance (LLC) stemming from the weakened Kondo peak, and when its coupling $\Gamma_s$ is bigger than the tunnel-coupling $\Gamma$ of two normal leads, the linear cross conductance (LCC) becomes negative in the Kondo region; for antiparallel configuration, increasing spin polarization further suppresses LLC but enhances LCC, i.e. causing larger negative values of LCC, since it is benefit for emergence of cross Andreev reflection; On the contrary, for parallel configuration, with increasing spin polarization, the LLC descends and greatly widens with the appearance of shoulders, and eventually splits into four peaks, and meanwhile the LCC reduces relatively rapidly to the normal conductance.