Realistic quantum critical point in one-dimensional two-impurity models

TL;DR

This paper demonstrates a robust quantum critical point in a one-dimensional two-impurity Anderson model, which is insensitive to certain symmetry breakings and has potential applications in spintronics.

Contribution

It reveals a new, symmetry-breaking resistant quantum critical point at specific impurity distances in a 1D model, expanding understanding of quantum phase transitions.

Findings

Existence of a new quantum critical point at specific impurity distances.

The critical point is robust against particle-hole and parity symmetry breaking.

Spectral functions show a jump at the critical point, indicating a phase transition.

Abstract

We show that the two-impurity Anderson model exhibits an additional quantum critical point at infinitely many specific distances between both impurities for an inversion symmetric one-dimensional dispersion. Unlike the quantum critical point previously established, it is robust against particle-hole or parity symmetry breaking. The quantum critical point separates a spin doublet from a spin singlet ground state and is, therefore, protected. A finite single-particle tunneling $t$ or an applied uniform gate voltage will drive the system across the quantum critical point. The discriminative magnetic properties of the different phases cause a jump in the spectral functions at low temperature, which might be useful for future spintronics devices. A local parity conservation will prevent the spin-spin correlation function from decaying to its equilibrium value after spin manipulations.