Correlation Driven Transport Asymmetries Through Coupled Spins

TL;DR

This study demonstrates how electronic transport measurements through coupled spins in a scanning tunneling microscope setup can reveal and control spin-spin correlations, providing a new experimental probe for quantum correlations.

Contribution

The paper introduces a method to measure and manipulate spin-spin correlations via transport asymmetries in a coupled spin system at the atomic scale.

Findings

Transport asymmetry correlates with spin-spin interactions.

Coupling strength controls the sign of correlations.

Zero-field asymmetry relates to ferromagnetic or antiferromagnetic states.

Abstract

Correlation is a fundamental statistical measure of order in interacting quantum systems. In solids, electron correlations govern a diverse array of material classes and phenomena such as heavy fermion compounds, Hunds metals, high-Tc superconductors, and the Kondo effect. Spin-spin correlations, notably investigated by Kaufman and Onsager in the 1940s 6, are at the foundation of numerous theoretical models but are challenging to measure experimentally. Reciprocal space methods can map correlations, but at the single atom limit new experimental probes are needed. Here, we determine the correlations between a strongly hybridized spin impurity and its electron bath by varying the coupling to a second magnetic impurity in the junction of a scanning tunneling microscope. Electronic transport through these coupled spins reveals an asymmetry in the differential conductance reminiscent of spin-polarized transport in a magnetic field. We show that at zero field, this asymmetry can be controlled by the coupling strength and is directly related to either ferromagnetic (FM) or antiferromagnetic (AFM) spin-spin correlations.