Coherent spin manipulation of individual atoms on a surface

Abstract

Achieving time-domain control of quantum states with atomic-scale spatial resolution in nanostructures is a long-term goal in quantum nanoscience and spintronics. Here, we demonstrate coherent spin rotations of individual atoms on a surface at the nanosecond time scale, using an all-electric scheme in a scanning tunneling microscope (STM). By modulating the atomically confined magnetic interaction between the STM tip and surface atoms, we drive quantum Rabi oscillations between spin-up and spin-down states in as little as ~20 nanoseconds. Ramsey fringes and spin echo signals allow us to understand and improve quantum coherence. We further demonstrate coherent operations on engineered atomic dimers. The coherent control of spins arranged with atomic precision provides a solid-state platform for quantum-state engineering and simulation of many-body systems.

Longitudinal and transverse electron paramagnetic resonance in a scanning tunneling microscope

“…Last, the experimental Rabi rate Ω is given in Fig. 3 (E and F) and ranges from about 100 MHz for TiH to about 1 MHz for Fe, consistent with the literature ( 12 ). This information allows us to perform a qualitative assessment of the different proposed EPR-STM mechanisms, as described below.…”

“…Despite early EPR-STM proposals using nonmagnetic tips (18,19) and recent experimental achievements using spin-polarized tips (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), the driving mechanism of EPR-STM remains under debate. The central idea of EPR is that rf photons excite unpaired electrons to a higher energy spin state, which can be probed experimentally.…”

“…In addition, the scattering of tunneling electrons at the spin center is relatively strong, thus disturbing the free evolution of the magnetic states. Reproducible EPR-STM experiments require the use of a magnetic tip (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), which further complicates the modeling of the STM junction. Several EPR-STM excitation and detection mechanisms have been proposed (19)(20)(21)(22)(23)(24)(25)(26), including modulation of the tunneling barrier by the rf electric field (23), breathing of the density of states mediated by spin-orbit coupling (19), spin torque due to tunneling electrons (24), and piezoelectric coupling (PEC) of the rf electric field to the magnetic adatom (22).…”

Combining Molecular Spintronics with Electron Paramagnetic Resonance: The Path Towards Single-Molecule Pulsed Spin Spectroscopy

“…Using advanced techniques, we can decouple the spins from the nuclear spin bath yielding competing quantum coherence times nearly reaching milliseconds, as it has been shown for graphenoids [282,283]. Addressing single molecules via EPR can then happen using magnetic scanning tunnelling tips [284]. The possibility of chemically grafting molecules allows us with endless possibilities to create an entirely new class of spintronic devices and come up with new theories on the physical properties of graphene nanoribbons.…”

Remote detection and recording of atomic-scale spin dynamics

“…Scanning tunneling microscopy (STM)-based atom manipulation allows for the assembly of artificial spin structures 6,7 : a technique that has enabled studies of collective magnetism ranging from the emergence of magnetic bistability [8][9][10] to spin waves 11 , phase transitions 12,13 and topologically protected edge states [14][15][16] . More recently, the implementation of electron spin resonance (ESR) 17 has led to coherent manipulation of combined atomic spin states 18 . However, by nature of the STM design, in each of these studies the effect of local tip-induced stimuli can only be probed there where they are generated.…”