Finite-size scaling exponents and entanglement in the two-level BCS model

TL;DR

This paper investigates the finite-size scaling behavior and entanglement characteristics of the two-level BCS model at quantum criticality, revealing nontrivial exponents and singular entanglement measures.

Contribution

It introduces a detailed analysis of finite-size scaling exponents and entanglement in the two-level BCS model using continuous unitary transformations.

Findings

Nontrivial scaling exponents at the quantum critical point

Singular behavior of the concurrence at the transition

Observable-dependent finite-size effects

Abstract

We analyze the finite-size properties of the two-level BCS model. Using the continuous unitary transformation technique, we show that nontrivial scaling exponents arise at the quantum critical point for various observables such as the magnetization or the spin-spin correlation functions. We also discuss the entanglement properties of the ground state through the concurrence which appears to be singular at the transition.