The quantum-classical metal

In a normal Fermi liquid, Landau's theory precludes the loss of single- fermion quantum coherence in the low-energy, low-temperature limit. For highly anisotropic, strongly correlated metals, there is no proof that this remains the case, and quantum coherence for transport in some directions may be lost intrinsically. This loss of coherence should stabilize an unusual, qualitatively anisotropic non-Fermi liquid, separated by a zero-temperature quantum phase transition from the Fermi liquid state and categorized by the unobservability of certain interference effects. There is compelling experimental evidence for this transition as a function of magnetic field in the metallic phase of the organic conductor (TMTSF)₂PF₆ (where TMTSF is tetramethyltetraselenafulvalene).