# Probing spin-dependent charge transport at single-nanometer length scales

## TL;DR

This paper introduces a novel method combining spin-polarized STM and molecular probes to visualize and analyze spin-dependent charge transport at nanometer scales, crucial for quantum device development.

## Contribution

It presents a new experimental approach for real-space detection of spin transport properties with nanometer resolution using SP-STM and MONA techniques.

## Key findings

- Reversal of current direction with tip magnetization in BiAg₂ surface state
- Single Gd cluster affects spin-dependent charge transport
- Proof-of-principle demonstration of the method's effectiveness

## Abstract

The coherent transport of charge and spin is one key requirement of future devices for quantum computing and communication. Scattering at defects or impurities may seriously reduce the coherence of quantum-mechanical states, thereby affecting device functionality. While numerous methods exist to experimentally assess charge transport, the real-space detection of a material's spin transport properties with nanometer resolution remains a challenge. Here we report on a novel approach which utilizes a combination of spin-polarized scanning tunneling microscopy (SP-STM) and the recently introduced molecular nanoprobe (MONA) technique. It relies on the local injection of spin-polarized charge carriers from a magnetic STM tip and their detection by a single surface-deposited phthalocyanine molecule via reversible electron-induced tautomerization events. Based on the particular electronic structure of the Rashba alloy BiAg$_2$ which is governed by a spin-momentum-locked surface state, we proof that the current direction inverses as the tip magnetization is reversed by an external field. In a proof-of-principle experiment we apply SP-MONA to investigate how a single Gd cluster influences the spin-dependent charge transport of the Rashba surface alloy.