Observation of a Structurally-Driven Mott Transition

We report a first-order structurally-driven Mott transition a t T=357 K in single crystal Ca2RuO4, an isomorph to the superconductor Sr2RuO4. A discontinuous jump in electrical resistivity with a concomitant change in magnetic moment is triggered by a pronounced structural transition from a high temperature tetragonal phase to a low temperature orthorhombic phase. We argue that t h e elastic energy associated with the reduction of the crystal s y m m e t r y coupled with the electronic delocalization energy represent p r imary forces that drive the observed Mott transition.