Comment on "$Z_{2}$ spin liquid phase on the kagome lattice: a new saddle point", by Tao Li [arXiv:1601.02165 (2016)]

TL;DR

This paper critically evaluates Tao Li's claim of a gapped $ ext{Z}_2$ spin liquid on the kagome lattice, using high-precision variational calculations to demonstrate that the state is a finite-size local minimum, supporting a gapless $U(1)$ Dirac spin liquid ground state.

Contribution

The authors provide highly accurate variational calculations that challenge previous claims, reaffirming the gapless $U(1)$ Dirac spin liquid as the true ground state.

Findings

$ ext{Z}_2$ spin liquid is a finite-size local energy minimum.

The $ ext{Z}_2$ state disappears with increasing system size.

Supports the gapless $U(1)$ Dirac spin liquid ground state.

Abstract

In a recent paper [arXiv:1601.02165], Tao Li claimed that a gapped $\mathbb{Z}_2$ spin liquid, obtained using projected Gutzwiller fermionic wave functions, can be stabilized in the Heisenberg model on the kagome lattice. We perform very accurate variational calculations and confirm with unprecedented accuracy the fact, that the $\mathbb{Z}_{2}$ spin liquid is a local energy minimum that goes away with system size, thus reaffirming the scenario of a gapless $U(1)$ Dirac spin liquid ground state.