Quantum criticality of Mott transition in organic materials

A many-body quantum system on the verge of instability between two competing ground states may exhibit quantum-critical phenomena, as has been intensively studied for magnetic systems. The Mott metal-insulator transition, a phenomenon that is central to many investigations of strongly correlated electrons, is also supposed to be quantum critical, although this has so far not been demonstrated experimentally. Here, we report experimental evidence for the quantum-critical nature of the Mott instability, obtained by investigating the electron transport of three organic systems with different ground states under continuously controlled pressure. The resistivity obeys the material-independent quantum-critical scaling relation bifurcating into a Fermi liquid or Mott insulator, irrespective of the ground states. Electrons on the verge of becoming delocalized behave like a strange quantum-critical fluid before becoming a Fermi liquid..