Measurements of Kondo and spin splitting in single-electron transistors

TL;DR

This paper introduces a new method to precisely measure spin splitting and Zeeman energy in single-electron transistors, revealing discrepancies with existing theoretical predictions about Kondo peak splitting at high magnetic fields.

Contribution

The study presents inelastic spin-flip cotunneling as a novel technique for accurate Zeeman energy measurement and compares it with Kondo peak splitting, highlighting unexpected results at high fields.

Findings

Inelastic spin-flip cotunneling yields precise Zeeman energy values.

Kondo peak splitting only appears above a threshold magnetic field.

High-field Kondo splitting exceeds theoretical predictions of twice the Zeeman energy.

Abstract

We measure the spin splitting in a magnetic field $B$ of localized states in single-electron transistors using a new method, inelastic spin-flip cotunneling. Because it involves only internal excitations, this technique gives the most precise value of the Zeeman energy $\Delta = \ZeemanE$. In the same devices we also measure the splitting with $B$ of the Kondo peak in differential conductance. The Kondo splitting appears only above a threshold field as predicted by theory. However, the magnitude of the Kondo splitting at high fields exceeds $2 \ZeemanE$ in disagreement with theory.