Phase diagram of a Heisenberg spin-Peierls model with quantum phonons

TL;DR

This paper uses an advanced density-matrix renormalization group method to map out the phase diagram of a quantum spin-phonon model, revealing a quantum phase transition relevant for real spin-Peierls materials.

Contribution

It introduces a new computational approach to analyze the phase diagram of a Heisenberg spin chain coupled to quantum phonons, highlighting the quantum phase transition and its universality class.

Findings

Quantum phase transition from gapless to gapped phase at non-zero spin-phonon coupling

Transition belongs to the same universality class as frustrated spin chains

Quantum phonons are essential for realistic modeling of spin-Peierls materials

Abstract

Using a new version of the density-matrix renormalization group we determine the phase diagram of a model of an antiferromagnetic Heisenberg spin chain where the spins interact with quantum phonons. A quantum phase transition from a gapless spin-fluid state to a gapped dimerized phase occurs at a non-zero value of the spin-phonon coupling. The transition is in the same universality class as that of a frustrated spin chain, which the model maps to in the anti-adiabatic limit. We argue that realistic modeling of known spin-Peierls materials should include the effects of quantum phonons.