Destruction of the Mott insulating ground state ofCa2RuO4by a structural transition

Abstract

We report a first-order phase transition at T M =357 K in single crystal Ca 2 RuO 4 , an isomorph to the superconductor Sr 2 RuO 4 . The discontinuous decrease in electrical resistivity signals the near destruction of the Mott insulating phase and is triggered by a structural transition from the low temperature orthorhombic to a high temperature tetragonal phase. The magnetic susceptibility, which is temperature dependent but not Curie-like decreases abruptly at T M and becomes less temperature dependent. Unlike most insulator to metal transitions, the system is not magnetically ordered in either phase, though the Mott insulator phase is antiferromagnetic below T N =110 K. PACS: 61.10 Nz, 71.30 +h,

Evolution of magnetism in single-crystalCa2Ru1−xIrxYuan1, Terzic2, Wang3 et al. 2015Phys. Rev. BSelf Cite493751View full textAdd to dashboardCite

“…A common characteristic of these materials is that underlying physical properties are critically linked to the lattice and orbital degrees of freedom and tend to exhibit a giant response to modest lattice changes. This is dramatically illustrated by Sr 2 RuO 4 and Ca 2 RuO 4 , where the former compound exhibits a prototypical p-wave superconducting state [1] that strongly contrasts with the more distorted structure (due to a smaller ionic radius r Ca < r Sr ) and first-order metal-insulator transition, T MI , observed for the latter compound [2,3].…”

“…Classic Mott insulators undergo simultaneous transitions to antiferromagnetic (AFM) order and an insulating state at T MI . However, Ca 2 RuO 4 undergoes AFM order at T N = 110 K T MI , [2] and is therefore a highly interesting and unique archetype of a metal-insulator transition that is strongly coupled to a structural transition from a high-T tetragonal to low-T orthorhombic distortion and is not driven by AFM exchange interactions [2,3,6,12].…”

Electronic structure of Mott-insulator CaCu 3 Ti 4 O 12 : Photoemission and inverse photoemission study

“…However, there exists many sophisticated situations rather than an ideal situation to be explained simply. For instance, the layered perovskite Ca 2 RuO 4 has shown the orbital selective Metal-insulator transition [6,7,8]. In Sr 2 IrO 4 , it has been reported that Mott insulator develops due to the strong spin-orbit interaction of Ir 5d-electrons [9].…”

Developments on Susceptibility and Magnetization Measurements under High Hydrostatic Pressure

“…At ambient pressure, this material is a Mott insulator which orders antiferromagnetically at T N = 110 K. At higher temperatures, Ca 2 RuO 4 goes through a structural phase transition at 357 K, from S-Pbca, where the octahedra is tilted and rotated, with a shortened c-axis, to LPbca type of structure in which the c-axis becomes elongated. This transition, in turn, induces a metal-insulator transition 3 .…”