Comment on arXiv:0811.1575 entitled "Quantum phase transitions in the Hubbard model on triangular lattice" by T. Yoshioka, A. Koga and N. Kawakami

TL;DR

This paper critiques a previous study on the Hubbard model on a triangular lattice, demonstrating that its phase boundary results are artifacts of small system size and providing corrected boundary estimates consistent with larger system extrapolations.

Contribution

It clarifies the accurate phase boundary between metallic and Mott insulating phases by correcting the finite-size effects in earlier work.

Findings

Previous phase boundary was an artifact of small lattice size.

Extrapolated phase boundary at U/t=5.2, consistent with larger system studies.

Corrected understanding of the metal-insulator transition in the model.

Abstract

We show that the phase boundary between the paramagnetic metal and the nonmagnetic Mott insulator for the Hubbard model on a triangular lattice obtained by Yoshioka et al. in arXiv:0811.1575 does not correctly represent that of the thermodynamic limit but is an artifact of the 6 by 6 lattice they rely on. After the system size extrapolation, the phase boundary is located at U/t=5.2 as proposed by Morita et al., J. Phys. Soc. Jpn. 71 (2008) 2109 and in contrast to Yoshioka et al. Here, U is the onsite Coulomb repulsion and t is the nearest-neighbor transfer.