Low-Energy Purification of Crystal Defects by Rydberg Excitons

TL;DR

This paper develops a multichannel theory for Rydberg exciton-impurity scattering in cuprous oxide, identifying a quantum regime at ultralow energies that enhances crystal purification by suppressing elastic and inelastic scattering.

Contribution

It introduces a detailed multichannel scattering model and predicts a low-energy quantum regime that improves impurity purification in Rydberg excitons.

Findings

High collision energies reduce purification efficiency due to elastic and inelastic scattering.

Ultralow collision energies favor a quantum regime with enhanced capture and suppressed scattering channels.

Degenerate two-photon excitation can access the low-energy regime for systematic studies.

Abstract

Recent experiments show that optically generated Rydberg excitons in cuprous oxide can neutralize charged impurities, strongly reducing stray electric fields and effectively purifying the crystal. Here, we develop a multichannel theory of Rydberg exciton-impurity scattering that resolves the competing roles of capture, elastic scattering, and inelastic transitions between excitonic states. We find that at high collision energies, as effective under conventional single-photon excitation, purification is reduced relative to Langevin capture. These collisions are accompanied by inelastic redistribution and dominant elastic scattering, including pronounced glory scattering, which suppress purification efficiency. We identify a quantum regime at ultralow collision energies favorable for purification, where only the s-wave contributes: capture is enhanced while elastic and inelastic channels are strongly suppressed. This regime can be accessed via degenerate two-photon excitation of even-parity Rydberg excitons with tunable recoil, additionally enabling the systematic exploration of exciton-impurity scattering over a wide range of collision energies beyond what is readily achievable in atomic counterparts in atomic gas experiments.