Infrared optical absorption spectra of CuO single crystals: Fermion-spinon band and dimensional crossover of the antiferromagnetic order

TL;DR

This study investigates the mid-infrared optical absorption spectra of CuO single crystals, revealing a fermion-spinon band and a dimensional crossover in antiferromagnetic order through polarized transmission measurements.

Contribution

It provides the first detailed interpretation of magnetic excitations in CuO spectra, highlighting the coexistence of spinon and magnon features and the dimensional crossover in magnetic behavior.

Findings

Observation of a Delta-shaped peak at 0.23 eV attributed to spinons.

Emergence of a 0.16 eV peak at low temperatures linked to two-magnon absorption.

Evidence of a dimensional crossover maintaining one-dimensional magnetic characteristics.

Abstract

We have obtained mid-infrared optical absorption spectra of the S=1/2 quasi one-dimensional CuO using polarized transmission measurement and interpreted the spectra in terms of phonon assisted magnetic excitations. When the electric field is parallel to the main antiferromagnetic direction a Delta shaped peak is observed with the maximum at 0.23eV which is attributed to spinons along Cu-O chains. At low temperatures in the antiferromagnetic phase another peak appears at 0.16eV which is attributed to two-magnon absorption but the spinon peak remains. This behavior is interpreted as due to a dimensional crossover where the low temperature three-dimensional magnetic phase keeps short range characteristics of a one-dimensional magnet.