Correlation-driven transport asymmetries through coupled spins in a tunnel junction

Area of Science:

• Condensed Matter Physics
• Quantum Materials Science
• Surface Science

Background:

• Spin-spin correlations are crucial for understanding strongly correlated materials but difficult to quantify at the atomic scale.
• Existing methods often measure collective effects, obscuring individual spin interactions.

Purpose of the Study:

• To directly quantify spin-spin correlations between a scanning tunnelling microscope (STM) tip impurity and its electron bath.
• To investigate the influence of coupling to a second spin impurity on these correlations.

Main Methods:

• Utilized a scanning tunnelling microscope with a spin-polarized tip.
• Varied the coupling strength between a strongly hybridized tip spin impurity and a second, weakly hybridized surface spin impurity.
• Analyzed electronic transport measurements, specifically differential conductance.

Main Results:

• Observed an asymmetry in differential conductance, analogous to spin-polarized transport in a magnetic field.
• Demonstrated that this zero-field asymmetry is tunable by controlling the inter-spin coupling strength.
• Correlated the observed asymmetry with either ferromagnetic or antiferromagnetic spin-spin correlations.

Conclusions:

• Developed a method to probe and control atomic-scale spin-spin correlations.
• Established a direct link between electronic transport asymmetry and the nature of spin correlations in quantum systems.
• Opened new avenues for designing and understanding materials with tailored magnetic properties.