Magnetic phases in the one-dimensional Kondo chain on a metallic surface

TL;DR

This paper investigates the low-temperature magnetic phases of a one-dimensional spin-1/2 chain coupled to a metal, revealing a phase diagram with Kondo-screened and dissipative phases separated by a quantum critical point.

Contribution

It provides the first detailed phase diagram of a 1D Kondo chain on a metallic surface, identifying a novel dissipative phase and quantum critical behavior.

Findings

Kondo singlet phase at strong coupling

Dissipative gapless spin excitations at weak/intermediate coupling

Quantum critical point with Wilson-Fisher universality class

Abstract

We study the low-temperature properties of a one-dimensional spin-1/2 chain of magnetic impurities coupled to a (normal) metal environment by means of anisotropic Kondo exchange. In the case of easy-plane anisotropy, we obtain the phase diagram of this system at T=0. We show that the in-plane Kondo coupling destabilizes the Tomonaga-Luttinger phase of the spin-chain, and leads to two different phases: i) At strong Kondo coupling, the spins in the chain form Kondo singlets and become screened by the metallic environment, and ii) At weak and intermediate Kondo coupling, we find a novel dissipative phase characterized by diffusive gapless spin excitations. The two phases are separated by a quantum critical point of the Wilson-Fisher universality class with dynamical exponent $z\simeq2$.