Kondo Phase Transitions of Magnetic Impurities in Carbon Nanotubes

TL;DR

This paper explores how magnetic impurities in carbon nanotubes can lead to unconventional Kondo phase transitions, influenced by nanotube properties and external tuning, revealing new quantum critical behaviors.

Contribution

It introduces a platform using CNTs with magnetic impurities to study Kondo physics, highlighting the effects of nanotube characteristics and external tuning on phase transitions.

Findings

Existence of a maximal radius for phase transitions in nonarmchair CNTs

Interference effects can suppress Kondo screening

Fermi energy tuning enables experimental access to quantum criticality

Abstract

We propose carbon nanotubes (CNTs) with magnetic impurities as a versatile platform to achieve unconventional Kondo physics, where the CNT bath is gapped by the spin-orbit interaction and surface curvature. While the strong-coupling phase is inaccessible for the special case of half-filled impurities in neutral armchair CNTs, the system in general can undergo quantum phase transitions to the Kondo ground state. The resultant position-specific phase diagrams are investigated upon variation of the CNT radius, chirality, and carrier doping, revealing several striking features, e.g., the existence of a maximal radius for nonarmchair CNTs to realize phase transitions, and an interference-induced suppression of the Kondo screening. We show that by tuning the Fermi energy via electrostatic gating, the quantum critical region can be experimentally accessed.