Scaling and Enhanced Symmetry at the Quantum Critical Point of the Sub-Ohmic Bose-Fermi Kondo Model

TL;DR

This paper investigates the finite temperature scaling at the quantum critical point of the sub-Ohmic Bose-Fermi Kondo model, revealing boundary conformal field theory characteristics despite the Hamiltonian's lack of conformal invariance.

Contribution

It demonstrates that the local properties at the quantum critical point of the sub-Ohmic BFKM exhibit boundary conformal field theory behavior, supported by Monte Carlo simulations and large-N analysis.

Findings

Scaling function matches boundary conformal field theory predictions

Correlators exhibit conformal invariance despite Hamiltonian's non-invariance

Results suggest local quantum criticality aligns with boundary conformal field theory

Abstract

We consider the finite temperature scaling properties of a Kondo-destroying quantum critical point in the Ising-anisotropic Bose-Fermi Kondo model (BFKM). A cluster-updating Monte Carlo approach is used, in order to reliably access a wide temperature range. The scaling function for the two-point spin correlator is found to have the form dictated by a boundary conformal field theory, even though the underlying Hamiltonian lacks conformal invariance. Similar conclusions are reached for all multi-point correlators of the spin-isotropic BFKM in a dynamical large-N limit. Our results suggest that the quantum critical local properties of the sub-ohmic BFKM are those of an underlying boundary conformal field theory.