Opposite pressure effects in the orbitally-induced Peierls phase transition systems CuIr2S4 and MgTi2O4

Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties submitted time 2017-11-27

张蕾

Abstract： The iso-spinel structural systems CuIr2S4 and MgTi2O4 exhibit phase transitions of the similar nature at #24; 230 K and #24; 260 K respectively, which are explained as an orbitally-induced Peierls phase transition. However, in this work, we uncover that applied pressure has opposite pressure effects on the phase transitions in CuIr2S4 and MgTi2O4. As pressure increases, the phase transition temperature (TMI ) for CuIr2S4 increases while that for MgTi2O4 decreases. In addition, the phase transition intensity becomes weaker for CuIr2S4 but gets stronger for MgTi2O4 under pressure. Our results indicate that the applied pressure suppresses the metallic phase in CuIr2S4, while enhances that in MgTi2O4. Combining the experimental observations with first-principle electronic structure calculations, we suggest that the opposite pressure effects in CuIr2S4 and MgTi2O4 originate from the different orbital ordering configurations (dxy, dyz/dxz) caused by different lattice distortions in these two systems. Our findings directly indicate that the interplay between the orbital and lattice degrees of freedom plays an important role in the orbitally-induced Peierls phase transition.

Peer Review Status:Awaiting Review

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