Entanglement Driven Phase Transitions in Spin-Orbital Models

TL;DR

This paper explores how von Neumann entropy spectra reveal quantum phase transitions in a one-dimensional spin-orbital model, uncovering novel entangled phases and demonstrating the entropy spectrum's utility in characterizing ground state changes.

Contribution

It introduces the von Neumann entropy spectral function as a new tool to identify and analyze quantum phase transitions and entanglement in spin-orbital models.

Findings

Discovery of a novel phase with Majumdar-Ghosh-like correlations triggered by entanglement.

Identification of a phase with coupled order parameters changing the transition from first-order to continuous.

Establishment of entropy spectra as effective indicators of ground state degeneracies and elementary excitations.

Abstract

To demonstrate the role played by the von Neumann entropy spectra in quantum phase transitions we investigate the one-dimensional anisotropic SU(2)$\otimes XXZ$ spin-orbital model with negative exchange parameter. In the case of classical Ising orbital interactions we discover an unexpected novel phase with Majumdar-Ghosh-like spin-singlet dimer correlations triggered by spin-orbital entanglement and having $k=\pi/2$ orbital correlations, while all the other phases are disentangled. For anisotropic $XXZ$ orbital interactions both spin-orbital entanglement and spin-dimer correlations extend to the antiferro-spin/alternating-orbital phase. This quantum phase provides a unique example of two coupled order parameters which change the character of the phase transition from first-order to continuous. Hereby we have established the von Neumann entropy spectral function as a valuable tool to identify the change of ground state degeneracies and of the spin-orbital entanglement of elementary excitations in quantum phase transitions.