Comment on "Topological quantum phase transitions of attractive spinless fermions in a honeycomb lattice" by Poletti D. et al

TL;DR

This paper critiques a mean-field study of attractive spinless fermions on a honeycomb lattice, showing that the predicted topological phases are unstable against phase separation, using advanced numerical methods.

Contribution

It demonstrates that the previously predicted topological phases are not stable without additional interactions, identifying the phase separation onset with iPEPS and exact diagonalization.

Findings

Predicted topological phases are unstable against phase separation.

Phase separation occurs at a lower attraction strength ($V_{ps} \\approx 1.7$) than previously thought.

Numerical methods reveal the true ground state stability in the model.

Abstract

In a recent letter [D. Poletti et al., EPL 93, 37008 (2011)] a model of attractive spinless fermions on the honeycomb lattice at half filling has been studied by mean-field theory, where distinct homogenous phases at rather large attraction strength $V>3.36$, separated by (topological) phase transitions, have been predicted. In this comment we argue that without additional interactions the ground states in these phases are not stable against phase separation. We determine the onset of phase separation at half filling $V_{ps}\approx 1.7$ by means of infinite projected entangled-pair states (iPEPS) and exact diagonalization.