The generic fixed point model for pseudo-spin-1/2 quantum dots in nonequilibrium: Spin-valve systems with compensating spin polarizations

TL;DR

This paper introduces a universal fixed point model for pseudo-spin-1/2 quantum dots in nonequilibrium, revealing how effective reservoirs with compensating spin orientations influence magnetization and current, especially at large bias voltages.

Contribution

It develops a generic fixed point framework for nonequilibrium pseudo-spin-1/2 quantum dots with arbitrary tunneling matrices, extending understanding of their universal properties.

Findings

Identification of a generic fixed point with compensating spin reservoirs

Analysis of magnetization and current dependence on magnetic field at high bias

Universal properties characterized for two-reservoir systems

Abstract

We study a pseudo-spin-1/2 quantum dot in the cotunneling regime close to the particle-hole symmetric point. For a generic tunneling matrix we find a generic fixed point with interesting nonequilibrium properties, characterized by effective reservoirs with compensating spin orientation vectors weighted by the polarizations and the tunneling rates. At large bias voltage we study the magnetic field dependence of the dot magnetization and the current. The fixed point can be clearly identified by analyzing the magnetization of the dot. We characterize in detail the universal properties for the case of two reservoirs.