Parity breaking and scaling behavior in the spin-boson model

TL;DR

This paper investigates parity breaking and critical scaling in the spin-boson model, revealing unique behaviors and challenging conventional spectral function assumptions, with broad analytical applicability.

Contribution

It provides a general analytical framework for understanding parity breaking and scaling in the spin-boson model, questioning traditional spectral function usage.

Findings

Identifies unique scaling behavior of magnetization and entanglement.

Shows that conventional spectral functions may be inadequate.

Reexamines the quantum phase transition justification.

Abstract

We study the breaking of parity in the spin-boson model and demonstrate unique scaling behavior of the magnetization and entanglement around the critical points for the parity breaking after suppressing the infrared divergence existing inherently in the spectral functions for Ohmic and sub-Ohmic dissipations. Our treatment is basically analytical and of generality for all types of the bath. We argue that the conventionally employed spectral function is not fully reasonable and the previous justification of quantum phase transition for localization needs to be more seriously reexamined.