# Valence bond solid and possible deconfined quantum criticality in an extended kagome lattice Heisenberg antiferromagnet

## TL;DR

This paper provides numerical evidence for a valence bond solid phase in an extended kagome lattice Heisenberg antiferromagnet, suggesting a possible continuous quantum phase transition and revealing complex competing phases.

## Contribution

It introduces the existence of an extended VBS phase near the Heisenberg point with detailed singlet patterning, and explores the nature of quantum phase transitions in this system.

## Key findings

- Identification of a diamond-like VBS pattern with a 12-site unit cell.
- Evidence for a possible continuous transition from magnetic order to VBS.
- Discovery of a spin-nematic-like phase near the ferromagnetic transition.

## Abstract

We present numerical evidence for the emergence of an extended valence bond solid (VBS) phase at $T=0$ in the kagome $S=1/2$ Heisenberg antiferromagnet with ferromagnetic further-neighbor interactions. The VBS is located at the boundary between two magnetically ordered regions and extends close to the nearest-neighbor Heisenberg point. It exhibits a diamond-like singlet covering pattern with a $12$-site unit-cell. Our results suggest the possibility of a direct, possibly continuous, quantum phase transition from the neighboring $\mathbf{q}=0$ coplanar magnetically ordered phase into the VBS phase. Moreover, a second phase which breaks lattice symmetries, and is of likely spin-nematic type, is found close to the transition to the ferromagnetic phase. The results have been obtained using numerical Exact Diagonalization. We discuss implications of our results on the nature of nearest-neighbor Heisenberg antiferromagnet.