Harnessing the Quantum Behavior of Spins on Surfaces

Abstract

out via microwave photons. [4] Spins in solid-state materials constitute another family of individual quantum systems where spin states with naturally quantized energy levels can be manipulated via magnetic fields. Physical realizations of solidstate spin systems include gate-defined quantum dots, single dopants in semiconductors such as phosphorus donors in silicon, and single defects in insulators such as nitrogen-vacancy centers in diamond. [5][6][7] Harnessing quantum resources at the nanoscale gives birth to the discipline of quantum-coherent nanoscience that may bring forth useful quantum nanodevices "at the bottom." [8,9] In this review, we focus on a new class of quantum spin systems, individual atomic and molecular spins on surfaces, which has the potential to produce quantum functionalities at the atomic scale. An STM is used to access this tiny length scale, where a sharp metallic tip is positioned in nanometer proximity to spin carriers on a surface to probe their properties through tunneling electrons. [10] Experiments with single atomic spins on material surfaces date back to the early days of low-temperature STM, when Yu-Shiba-Rusinov states and a Kondo resonance were measured in individual magnetic atoms on bulk superconductors [11] and noble metals, [12,13] respectively. STM has also been extensively used on single molecular spins to characterize molecular structures, [14][15][16] probe and modify their electronic and magnetic properties, [17][18][19] and investigate their classical and quantum applications. [19][20][21] Following early STM experiments on single spins, the desire to further control and magnetically image individual spins has prompted the developments of new local probe techniques such as spinpolarized STM, [22] inelastic-tunneling-based spin-flip spectroscopy, [23] electrical pump-probe measurements, [24] and various innovative forms of force and magnetic microscopy. [25][26][27][28] An exciting development in recent years is the incorporation of coherent spin control in atomic-scale microscopy. The need to coherently manipulate and measure individual spins at this length scale necessitates all-electrical protocols with Angstrom precision. These stringent requirements are met by drawing on powerful methodologies from material and quantum sciences, that is, STM's abilities to build nanostructures atom-by-atom and selectively sense individual spin-carrying atoms, as well as electron spin resonance's (ESR's) ability to coherently control electron spin states via electromagnetic waves. This unique combination has so far enabled the quantum control of single electron spins of atoms [29][30][31][32][33] and molecules, [34] as well as the manipulation of single nuclear spins through hyperfine interactions. [35] Quantum coherence can be increased using singlet-triplet The desire to control and measure individual quantum systems such as atoms and ions in a vacuum has led to significant scientific and engineering developments in the past decades that form the basis of today's quantum infor...

Anisotropic Hyperfine Interaction of Surface-Adsorbed Single Atoms

“…Scanning tunneling microscopy (STM) with ESR capabilities offers a new appealing platform for in situ characterization of individual spin-carrying atoms and molecules. − ESR-STM spectroscopy offers tens of nanoelectrovolt energy resolution, far beyond traditional STM bias spectroscopy, − thus allowing for probing hyperfine interactions at the atomic scale. , When combined with STM’s single-atom selectivity, hyperfine interactions from single atoms with different isotopes and different binding sites can be individually determined without spatial averaging …”

Lanthanide-directed metal–organic coordination networks

“…Thanks to the versatility of coordination chemistry, the chemical combinations by selecting appropriate lanthanide elements, linkers and substrates seem endless, envisioning a promising pathway for the emerging field of magnetic lanthanide-directed metallosupramolecular architectures on surfaces, with great potential impact both in information storage and quantum information. 122,123…”

Development of a scanning tunneling microscope for variable temperature electron spin resonance

“…The spectral resolution can be significantly enhanced by ESR spectroscopy in STM. In ESR-STM, the energy is measured with respect to the frequency of an applied RF field and thus the energy resolution is limited only by the spin dynamics of the objects such as spin relaxation and coherence times 15 . For the ESR measurement, a spin-polarized tip is prepared by picking up several Fe atoms to the tip (typically 3-10 Fe atoms) and checking its polarization by dI/dV curves of TiH O or TiH B that show 28,29,31 .…”

“…Conventional ensemble ESR, however, requires at least 10 7 spins (10 12 for nuclear spins) to get strong enough signals [11][12][13] , while its spectroscopic resolution is not a) Corresponding authors limited by temperature. The integration of ESR with STM maximizes the powerful benefits of both approaches, and the single spin ESR detection with atomic resolution has been exclusively achieved by ESR spectroscopy in STM 14,15 .…”