Spin decoherence of magnetic atoms on surfaces

TL;DR

This paper reviews recent experimental and theoretical advances in understanding spin decoherence of magnetic atoms on surfaces, focusing on measurement techniques and physical mechanisms like Kondo interaction and spin-phonon coupling.

Contribution

It provides a comprehensive overview of spin decoherence mechanisms and discusses new measurement techniques such as electrically driven STM spin resonance.

Findings

Measurement of spin relaxation time $T_1$ using spin-polarized STM tips.

Direct measurement of spin decoherence time $T_2$ via electrically driven STM resonance.

Analysis of physical mechanisms including Kondo interaction, spin-phonon coupling, and Johnson noise.

Abstract

We review the problem of spin decoherence of magnetic atoms deposited on a surface. Recent breakthroughs in scanning tunnelling microscopy (STM) make it possible to probe the spin dynamics of individual atoms, either isolated or integrated in nanoengineered spin structures. Transport pump and probe techniques with spin polarized tips permit measuring the spin relaxation time $T_1$, while novel demonstration of electrically driven STM single spin resonance has provided a direct measurement of the spin decoherence time $T_2$ of an individual magnetic adatom. Here we address the problem of spin decoherence from the theoretical point of view. First we provide a short general overview of decoherence in open quantum systems and we discuss with some detail ambiguities that arise in the case of degenerate spectra, relevant for magnetic atoms. Second, we address the physical mechanisms that allows probing the spin coherence of magnetic atoms on surfaces. Third, we discuss the main spin decoherence mechanisms at work on a surface, most notably, Kondo interaction, but also spin-phonon coupling and dephasing by Johnson noise. Finally, we propose some schemes to engineer spin decoherence.