Harnessing the Quantum Behavior of Spins on Surfaces

Abstract

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 information science. Single atoms and molecules on surfaces, on the other hand, are heavily investigated by physicists, chemists, and material scientists in search of novel electronic and magnetic functionalities. These two paths crossed in 2015 when it was first clearly demonstrated that individual spins on a surface can be coherently controlled and read out in an all-electrical fashion. The enabling technique is a combination of scanning tunneling microscopy (STM) and electron spin resonance (ESR), which offers unprecedented coherent controllability at the Angstrom length scale. This review aims to illustrate the essential ingredients that allow the quantum operations of single spins on surfaces. Three domains of applications of surface spins, namely quantum sensing, quantum control, and quantum simulation, are discussed with physical principles explained and examples presented. Enabled by the atomically-precise fabrication capability of STM, single spins on surfaces might one day lead to the realization of quantum nanodevices and artificial quantum materials at the atomic scale.

Interplay of magnetic states and hyperfine fields of iron dimers on MgO(001)

“…On the other hand, our findings question the use of the hyperfine Hamiltonian, equation ( 1), usually amended with conventional Heisenberg exchange interaction to describe the interplay of magnetic coupling and hyperfine interaction, which is not anymore a constant, in multi-atomic structures. To address the latter aspect, we proposed an extended hyperfine-Heinseberg Hamiltonian, equation (3), where the hyperfine interaction is proportional to the dot product of the spin moments, as motivated from multiple-scattering theory. Our calculations confirm that the angular dependence is reasonable for a wide range of angles around the value obtained for the ferromagnetic state.…”

“…Magnetic adatoms on thin insulating layers have attracted a lot of attention due to potential applications in magnetic storage [1,2] and quantum coherent manipulation [3,4]. Thin insulating layers [1,2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are very appealing for qubits realizations on the basis of adatoms since their interaction with the substrate's conduction electrons is strongly reduced, which should favor coherence.…”

Interplay of magnetic states and hyperfine fields of iron dimers on MgO(001)

“…Magnetic adatoms on thin insulating layers have attracted a lot of attention due to potential applications in magnetic storage [4,5] and quantum computation [6]. Thin insulating layers [7,8,9,10,11,12,13,14,5,15,16,17,4,18,19,20,21,22] are very appealing for qubits realizations on the basis of adatoms since their interaction with the substrate's conduction electrons is strongly reduced, which should favor coherence.…”