Abstract
We introduce the Rydberg composite, a new class of Rydberg matter where a single Rydberg atom is interfaced with a dense environment of neutral ground state atoms. The properties of the composite depend on both the Rydberg excitation, which provides the gross energetic and spatial scales, and the distribution of ground state atoms within the volume of the Rydberg wave function, which sculpt the electronic states. The latter range from the “trilobites,” for small numbers of scatterers, to delocalized and chaotic eigenstates, for disordered scatterer arrays, culminating in the dense scatterer limit in symmetry-dominated wave functions which promise good control in future experiments. We discuss one-, two-, and three-dimensional arrangements of scatterers using different theoretical methods, enabling us to obtain scaling behavior for the regular spectrum and measures of chaos and delocalization in the disordered regime. We also show that analogous quantum dot composites can elucidate in particular the dense scatterer limit. Thus, we obtain a systematic description of the composite states. The two-dimensional monolayer composite possesses the richest spectrum with an intricate band structure in the limit of homogeneous scatterers, experimentally accessible with pancake-shaped condensates.
7 More- Received 3 September 2019
- Accepted 24 June 2020
DOI:https://doi.org/10.1103/PhysRevX.10.031046
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
In a Rydberg atom, one or more electrons are excited to a very high state. In this state, the wave function of the excited electron occupies a relatively large volume (easily times larger than the ground state) and has highly degenerate energies. Here, we show that this degeneracy can be lifted in a controlled manner by filling the particle’s wave function with other neutral atoms, or “scatterers,” creating a system we call a Rydberg composite.
By smoothly tuning the number of scatterers in the composite, the energy degeneracy can be lifted in two different ways. When just a few scatterers are present, each additional scatterer causes one of the energy levels to deviate from the degenerate value until all energy levels are no longer degenerate. At the opposite extreme of many scatterers, the density of scatterers becomes so dense that the Rydberg wave function no longer “sees” individual scatterers but rather a homogenous fog of them. The geometry of this fog is incompatible with any Rydberg wave function and therefore breaks the degeneracy. If the geometry is planar, for example, then the Rydberg spectrum changes to one with well-structured energy bands, which we predict to be observable in a dense pancake-shaped Bose-Einstein condensate.
Analogous composites may be formed with suitable highly excited quantum dot states. Generally, by varying the scatterer density, excitation composites introduce an approach to systematically create and describe properties of systems that occupy territory between atomic and condensed matter.