Magnetism of the N=42 kagome lattice antiferromagnet

TL;DR

This study uses large-scale numerical methods to explore thermodynamic properties of the N=42 kagome lattice antiferromagnet, revealing unique features caused by frustration and flat magnon bands.

Contribution

It provides the first large-scale finite-temperature analysis of the N=42 kagome antiferromagnet, highlighting the effects of frustration on thermodynamic behavior.

Findings

Finite-size scaling of specific heat shows a low-temperature shoulder.

Asymmetric melting of the 1/3 magnetization plateau observed.

Characteristic features in specific heat due to flat magnon band.

Abstract

For the paradigmatic frustrated spin-half Heisenberg antiferromagnet on the kagome lattice we performed large-scale numerical investigation of thermodynamic functions by means of the finite-temperature Lanczos method for system sizes of up to N=42. We present the dependence of magnetization as well as specific heat on temperature and external field and show in particular that a finite-size scaling of specific heat supports the appearance of a low-temperature shoulder below the major maximum. This seems to be the result of a counterintuitive motion of the density of singlet states towards higher energies. Other interesting features that we discuss are the asymmetric melting of the 1/3 magnetization plateau as well the field dependence of the specific heat that exhibits characteristic features caused by the existence of a flat one-magnon band. By comparison with the unfrustrated square-lattice antiferromagnet the tremendous role of frustration in a wide temperature range is illustrated.