Comment on "Josephson Current through a Nanoscale Magnetic Quantum Dot"

In a recent work [Phys. Rev. Lett. 93, 047002 (2004)], Siano and Egger (SE) studied Josephson current through a quantum dot in the Kondo regime using the quantum Monte Carlo (QMC) method. Several of their results were inconsistent with those from the numerical renormalization group (NRG) calculations [Phys. Rev. B 70, R020502 (2004); J. Phys. Soc. Jpn. 69, 1812 (2000)] among other previous studies. The results of SE are not reliable for the following two reasons: (i) The definition of the Kondo temperature was not correct; (ii) There were substantial fintie-temperature effects.