Low Energy Singlets in the Heisenberg Kagome Antiferromagnet

TL;DR

This paper investigates the low-energy singlet states in the spin-1/2 Heisenberg Kagome antiferromagnet, revealing a ground state with dimer order and explaining experimental observations of specific heat and singlet density.

Contribution

It introduces a mapping to a spin-pseudospin Hamiltonian and identifies a columnar dimer ground state with fluctuating dimer orientations.

Findings

Ground state exhibits columnar dimer order.

High density of low-energy singlets explained.

Non-magnetic T-squared specific heat observed experimentally.

Abstract

The spin half Heisenberg antiferromagnet on the Kagome lattice, is mapped by Contractor Renormalization to a Spin-Pseudospin Hamiltonian on the triangular superlattice. Variationally, we find a ground state with columnar dimer order. Dimer orientation fluctuations are described by an effective O(2) model at energies above an exponentially suppressed clock mass scale. Our results explain the large density of low energy singlets observed numerically, and the non magnetic T-squared specific heat observed experimentally.