Interaction of Rydberg atoms with surfaces

Abstract

Abstract. The interface of neutral Rydberg atoms in the gas phase with a solid surface is of interest in many fields of modern research. This interface poses a particular challenge for any application in which Rydberg atoms are close to a substrate but also opens up the possibility of studying properties of the surface material itself through the atomic response. In this review the focus is on the process of electron tunneling from the excited state into the substrate that occurs when a Rydberg atom is located in front of a surface at a range of a few hundred nm and is demonstrated with a metallic surface. It is shown how variations in this ionisation mechanism can provide a powerful tool to probe imagecharge effects, measure small superficial electric stray or patch fields and how charge transfer from the Rydberg atom can be in resonance with energetically discrete surface states. Rydberg atoms at surfaces and interfacesWhen atoms are excited into states of high principal quantum number n their properties are exaggerated and long-range interactions lead to a strong coupling with their environment. The electron cloud is greatly expanded compared to the ground state (∝ n 2 ) which results in a large polarisability of a Rydberg state (∝ n 7 ) causing a strong response to electric fields [1]. In terms of a classical dipole, the positive core and negative electron are widely separated giving these excited states a large dipole moment, by which Rydberg atoms exhibit interactions over great distances (∼ μm), where the interactions can be controlled externally. The range of exotic properties makes them an interesting subject in various fields of research, Rydberg atoms are used in cavity quantum electrodynamics [2,3], in controlled chemical reactions by mechanical manipulation [4], serve as a model system for dipole-mediated energy transport in biological systems [5], can be used as a non-linear medium to mediate single-photon interactions [6,7] and have been proposed in several ways for quantum information processing [9][10][11][12]. However, this also means that the strong interaction will not be limited to surrounding atoms but that they also couple to condensed matter, bulk surfaces, in the vicinity. See Fig. 1 for an overview of Rydberg-surface interactions.a

Pulsed production of antihydrogen

“…The interaction of a Rydberg H with a metallic surface is first due to the electrostatic interaction with its induced image charge. The large dipole of a Rydberg state induces a charge polarization in a metallic bulk that results in an attractive net force 42 . At the smaller end of the range of separations, the influence of the image charge interactions becomes stronger, and the positron could potentially be able to pass over or tunnel through the potential barrier into the conduction band producing annihilation.…”

Casimir-Polder interactions of Rydberg atoms with graphene-based van der Waals heterostructures

“…n 1. The size of Rydberg atoms is proportional to n 2 , and can be a micron when n ∼ 90, resulting in weakly bound valence electrons and high electric polarizability, which in turn causes strong interactions with nearby surfaces [68]. The lifetime associated with spontaneous emission, i.e.…”

Copper plasmonics with excitons

“…Furthermore, another reason to consider only the lowest P-excitonic states (n=2,3) is the interaction of excitons with metallic surfaces. As mentioned above, excitons with high principal quantum number are very sensitive to external electric fields, including electrostatic fields at metal-dielectric interface [25], leading to ionisation of excitons that are separated from the metal surface by a distance comparable to exciton radius. Thus, for example, one can expect that n = 2 exciton in Cu 2 O is strongly affected by the metallic environment when located closer than approximately 6 nm from the metal-dielectric interface.…”