  We investigate the chiral phase transition at finite temperature (T) in
colour SU(Nc=3) Quantum Chromodynamics (QCD) with six species of fermions
(Nf=6) in the fundamental representation by using lattice QCD with improved
staggered fermions. By considering lattices with several temporal extensions
Nt, we observe asymptotic scaling for Nt > 4. We then extract the dimensionless
ratio Tc/Lambda_L (Lambda_L = Lattice Lambda-parameter) for Nf = 6 and Nf = 8,
the latter relying on our earlier results. Further, we collect the critical
couplings beta^c for the chiral phase transition at Nf = 0 (quenched), and Nf =
4 at a fixed Nt = 6. The results are consistent with enhanced fermionic
screening at larger Nf. The Tc/Lambda_L depends very mildly on Nf in the Nf = 0
- 4 region, starts increasing at Nf = 6, and becomes significantly larger at Nf
= 8, close to the edge of the conformal window. We discuss interpretations of
these results as well as their possible interrelation with preconformal
dynamics in the light of a functional renormalization group analysis.
