One-dimensional physics of the frustrated quantum magnet PHCC

TL;DR

This paper combines density-functional calculations and quantum simulations to model the magnetic behavior of the frustrated quantum magnet PHCC as a one-dimensional zigzag spin chain, accurately describing its susceptibility, magnetization, and excitation spectrum.

Contribution

It introduces a detailed one-dimensional frustrated spin chain model for PHCC that quantitatively matches experimental magnetic properties and predicts bound states of triplets.

Findings

Model accurately reproduces magnetic susceptibility and magnetization.

Describes the dispersion of the single-triplet band and continuum merging.

Predicts sharp bound and anti-bound states of two triplets.

Abstract

We report a comprehensive microscopic study of the frustrated quantum magnet PHCC, (C$_4$H$_{12}$N$_2$)Cu$_2$Cl$_6$, using density-functional band-structure calculations combined with numerical quantum many-body simulations of the underlying spin Hamiltonian. We show that the magnetism of PHCC is captured by a one-dimensional model of the frustrated spin chain with alternating nearest-neighbor couplings ($J_1=23.1$ K, $J_1'=7.0$ K) and uniform next-nearest-neighbor couplings ($J_2=13.9$ K). This model, which can also be thought of as a zigzag ladder, provides a quantitative description of the magnetic susceptibility and the magnetization process, and accounts for the observed dispersion of the single-triplet band and its merging into a continuum near the Brillouin zone center. We also make predictions for the existence of sharp bound (anti-bound) states of two triplets, below (above) the bottom (upper) edge of the two-particle scattering continuum.