Magnetic Field Probing of an SU(4) Kondo Resonance in a Single Atom Transistor

TL;DR

This paper investigates the magnetic field-induced transition from an SU(4) to SU(2) Kondo ground state in a single-atom transistor, revealing how magnetic fields influence spin and orbital symmetries in quantum impurity systems.

Contribution

It demonstrates both experimentally and theoretically how to tune a symmetry transition from SU(4) to SU(2) in a dopant-based nano-device using magnetic fields.

Findings

Observation of SU(4) to SU(2) symmetry transition with magnetic field

Experimental validation of theoretical models of Kondo states

Identification of the role of spin and orbital degrees of freedom

Abstract

Semiconductor nano-devices have been scaled to the level that transport can be dominated by a single dopant atom. In the strong coupling case a Kondo effect is observed when one electron is bound to the atom. Here, we report on the spin as well as orbital Kondo ground state. We experimentally as well than theoretically show how we can tune a symmetry transition from a SU(4) ground state, a many body state that forms a spin as well as orbital singlet by virtual exchange with the leads, to a pure SU(2) orbital ground state, as a function of magnetic field. The small size and the s-like orbital symmetry of the ground state of the dopant, make it a model system in which the magnetic field only couples to the spin degree of freedom and allows for observation of this SU(4) to SU(2) transition.