Perfect Metal Phases of One-Dimensional and Anisotropic Higher-Dimensional Systems

We show that a 1D quantum wire with $23$ channels of interacting fermions has a perfect metal phase in which all weak perturbations that could destabilize this phase are irrelevant. Consequently, weak disorder does not localize it, a weak periodic potential does not open a gap, and contact with a superconductor also fails to open a gap. Similar phases occur for $N\ge 24$ channels of fermions, except for $N=25$, and for $8k$ channels of interacting bosons, with $k\ge 3$. Arrays of perfect metallic wires form higher-dimensional fermionic or bosonic perfect metals, albeit highly-anisotropic ones.