Spin chain on a metallic surface: Dissipation-induced order vs. Kondo entanglement

TL;DR

This paper investigates a spin-1/2 Heisenberg chain coupled to a metallic surface, revealing a quantum transition between antiferromagnetic order and heavy-fermion behavior driven by dissipation and Kondo screening.

Contribution

It provides a negative-sign-free quantum Monte Carlo simulation of a transition between antiferromagnetic and heavy-fermion phases in a spin chain on a metallic surface.

Findings

Long-range antiferromagnetic order induced by dissipation at weak Kondo coupling.

Presence of Landau-damped Goldstone modes in the spin structure factor.

Heavy bands near the Fermi energy indicating heavy-fermion behavior.

Abstract

We explore the physics of a spin-1/2 Heisenberg chain with Kondo interaction, $J_k$, to a two-dimensional electron gas. At weak $J_k$ the problem maps onto a Heisenberg chain locally coupled to a dissipative Ohmic bath. At the decoupled fixed point, the dissipation is a marginally relevant perturbation and drives long-range antiferromagnetic order along the chain. In the dynamical spin structure factor we observe a quadratic low-energy dispersion akin to Landau-damped Goldstone modes. At large $J_k$ Kondo screening dominates, and the spin correlations of the chain inherit the power law of the host metal, akin to a paramagnetic heavy Fermi liquid. In both phases we observe heavy bands near the Fermi energy in the composite-fermion spectral function. Our results, obtained from auxiliary-field quantum Monte Carlo simulations, provide a unique negative-sign-free realization of a quantum transition between an antiferromagnetic metal and a heavy-fermion metal. We discuss the relevance of our results in the context of scanning tunneling spectroscopy experiments of magnetic adatom chains on metallic surfaces.