Atomic Collapse and Quasi-Rydberg States in Graphene

TL;DR

This paper explores atomic collapse phenomena in graphene, revealing Rydberg-like resonance states caused by charge impurities, with implications for transport, local properties, and the Kondo effect.

Contribution

It demonstrates that divalent and trivalent impurities in graphene can realize atomic collapse states, providing a platform for studying supercritical charge effects in Dirac materials.

Findings

Observation of Rydberg-like resonance states in graphene

Enhanced Kondo effect due to impurity-induced resonances

Distinct signatures in transport and local measurements

Abstract

Charge impurities in graphene can host an infinite family of Rydberg-like resonance states of massless Dirac particles. These states, appearing for supercritical charge, are described by Bohr-Sommerfeld quantization of collapsing classical trajectories that descend on point charge, in analogy to Rydberg states relation with planetary orbits. We argue that divalent and trivalent charge impurities in graphene is an ideal system for realization of this atomic collapse regime. Strong coupling of these states to the Dirac continuum via Klein tunneling leads to striking resonance effects with direct signatures in transport, local properties and enhancement of the Kondo effect.