Special CPM Seminar

Toward Single Atom Qubits on a Surface: ESR in the STM

William Paul

IBM Research

Single Fe atoms placed on MgO films have exceptional magnetic properties: Their spin relaxation lifetime can extend to many milliseconds, and their quantum state can be coherently manipulated by RF electric fields. In this talk, we will discuss a scanning tunneling microscopy (STM) investigation of the dynamics of spin-relaxation and the electric field-driven spin resonance of individual Fe atoms adsorbed to MgO. We show that the T1 lifetime of single Fe atoms on MgO can exceed 10 ms, and can be tuned by adjusting the thickness of insulating MgO film separating it from a silver substrate. Next, we demonstrate electron spin resonance (ESR) of an individual single Fe atom, driven by a gigahertz frequency electric field applied across the tip-sample junction, and detected by a spin-polarized tunneling current [1]. The principle parameters of the spin resonance experiment, namely the phase coherence time T2 and the Rabi rate, are characterized for Fe atoms adsorbed to the monolayer MgO film. We can furthermore use the Fe atom as a sensor of the local magnetic environment (which can be positioned with atomic precision by the STM tip) and we demonstrate its remarkable capabilities in measuring magnetic interactions with nano-electronvolt energy and picometer spatial resolutions. We conclude with an outlook toward quantum devices built atom-by-atom on surfaces.

[1] Baumann and Paul et al., Science 350, 417 (2015)